diff --git a/src/main/java/org/apache/datasketches/count/CountMinSketch.java b/src/main/java/org/apache/datasketches/count/CountMinSketch.java
new file mode 100644
index 000000000..36bea38cf
--- /dev/null
+++ b/src/main/java/org/apache/datasketches/count/CountMinSketch.java
@@ -0,0 +1,421 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.datasketches.count;
+
+import org.apache.datasketches.common.Family;
+import org.apache.datasketches.common.SketchesArgumentException;
+import org.apache.datasketches.common.SketchesException;
+import org.apache.datasketches.hash.MurmurHash3;
+import org.apache.datasketches.tuple.Util;
+
+import java.io.ByteArrayOutputStream;
+import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
+import java.util.Random;
+
+
+public class CountMinSketch {
+  private final byte numHashes_;
+  private final int numBuckets_;
+  private final long seed_;
+  private final long[] hashSeeds_;
+  private final long[] sketchArray_;
+  private long totalWeight_;
+
+
+  private enum Flag {
+    IS_EMPTY;
+
+    int mask() {
+      return 1 << ordinal();
+    }
+  }
+
+  /**
+   * Creates a CountMin sketch with given number of hash functions and buckets,
+   * and a user-specified seed.
+   *
+   * @param numHashes The number of hash functions to apply to items
+   * @param numBuckets Array size for each of the hashing function
+   * @param seed The base hash seed
+   */
+  CountMinSketch(final byte numHashes, final int numBuckets, final long seed) {
+    numHashes_ = numHashes;
+    numBuckets_ = numBuckets;
+    seed_ = seed;
+    hashSeeds_ = new long[numHashes];
+    sketchArray_ = new long[numHashes * numBuckets];
+    totalWeight_ = 0;
+
+    if (numBuckets < 3) {
+      throw new SketchesArgumentException("Using fewer than 3 buckets incurs relative error greater than 1.");
+    }
+
+    // This check is to ensure later compatibility with a Java implementation whose maximum size can only
+    // be 2^31-1.  We check only against 2^30 for simplicity.
+    if (numBuckets * numHashes >= 1 << 30) {
+      throw new SketchesArgumentException("These parameters generate a sketch that exceeds 2^30 elements. \n" +
+          "Try reducing either the number of buckets or the number of hash functions.");
+    }
+
+    Random rand = new Random(seed);
+    for (int i = 0; i < numHashes; i++) {
+      hashSeeds_[i] = rand.nextLong();
+    }
+  }
+
+  private long[] getHashes(byte[] item) {
+    long[] updateLocations = new long[numHashes_];
+
+    for (int i = 0; i < numHashes_; i++) {
+      long[] index = MurmurHash3.hash(item, hashSeeds_[i]);
+      updateLocations[i] = i * (long)numBuckets_ + Math.floorMod(index[0], numBuckets_);
+    }
+
+    return updateLocations;
+  }
+
+  /**
+   * Checks if the CountMinSketch has processed any items.
+   * @return True if the sketch is empty, otherwise false.
+   */
+  public boolean isEmpty() {
+    return totalWeight_ == 0;
+  }
+
+  /**
+   * Returns the number of hash functions used in this sketch.
+   * @return The number of hash functions.
+   */
+  public byte getNumHashes_() {
+    return numHashes_;
+  }
+
+  /**
+   * Returns the number of buckets per hash function.
+   * @return The number of buckets.
+   */
+  public int getNumBuckets_() {
+    return numBuckets_;
+  }
+
+  /**
+   * Returns the hash seed used by this sketch.
+   * @return The seed value.
+   */
+  public long getSeed_() {
+    return seed_;
+  }
+
+  /**
+   * Returns the total weight of all items inserted into the sketch.
+   * @return The total weight.
+   */
+  public long getTotalWeight_() {
+    return totalWeight_;
+  }
+
+  /**
+   * Returns the relative error of the sketch.
+   * @return The relative error.
+   */
+  public double getRelativeError() {
+    return Math.exp(1.0) / (double)numBuckets_;
+  }
+
+  /**
+   * Suggests an appropriate number of hash functions to use for a given confidence level.
+   * @param confidence The desired confidence level between 0 and 1.
+   * @return Suggested number of hash functions.
+   */
+  public static byte suggestNumHashes(double confidence) {
+    if (confidence < 0 || confidence > 1) {
+      throw new SketchesException("Confidence must be between 0 and 1.0 (inclusive).");
+    }
+    int value = (int) Math.ceil(Math.log(1.0 / (1.0 - confidence)));
+    return (byte) Math.min(value, 127);
+  }
+
+  /**
+   * Suggests an appropriate number of buckets per hash function for a given relative error.
+   * @param relativeError The desired relative error.
+   * @return Suggested number of buckets.
+   */
+  public static int suggestNumBuckets(double relativeError) {
+    if (relativeError < 0.) {
+      throw new SketchesException("Relative error must be at least 0.");
+    }
+    return (int) Math.ceil(Math.exp(1.0) / relativeError);
+  }
+
+  /**
+   * Updates the sketch with the provided item and weight.
+   * @param item The item to update.
+   * @param weight The weight of the item.
+   */
+  public void update(final long item, final long weight) {
+    byte[] longByte = ByteBuffer.allocate(8).putLong(item).array();
+    update(longByte, weight);
+  }
+
+  /**
+   * Updates the sketch with the provided item and weight.
+   * @param item The item to update.
+   * @param weight The weight of the item.
+   */
+  public void update(final String item, final long weight) {
+    if (item == null || item.isEmpty()) {
+      return;
+    }
+    final byte[] strByte = item.getBytes(StandardCharsets.UTF_8);
+    update(strByte, weight);
+  }
+
+  /**
+   * Updates the sketch with the provided item and weight.
+   * @param item The item to update.
+   * @param weight The weight of the item.
+   */
+  public void update(final byte[] item, final long weight) {
+    if (item.length == 0) {
+      return;
+    }
+
+    totalWeight_ += weight > 0 ? weight : -weight;
+    long[] hashLocations = getHashes(item);
+    for (long h : hashLocations) {
+      sketchArray_[(int) h] += weight;
+    }
+  }
+
+  /**
+   * Returns the estimated frequency for the given item.
+   * @param item The item to estimate.
+   * @return Estimated frequency.
+   */
+  public long getEstimate(final long item) {
+    byte[] longByte = ByteBuffer.allocate(8).putLong(item).array();
+    return getEstimate(longByte);
+  }
+
+  /**
+   * Returns the estimated frequency for the given item.
+   * @param item The item to estimate.
+   * @return Estimated frequency.
+   */
+  public long getEstimate(final String item) {
+    if (item == null || item.isEmpty()) {
+      return 0;
+    }
+
+    final byte[] strByte = item.getBytes(StandardCharsets.UTF_8);
+    return getEstimate(strByte);
+  }
+
+  /**
+   * Returns the estimated frequency for the given item.
+   * @param item The item to estimate.
+   * @return Estimated frequency.
+   */
+  public long getEstimate(final byte[] item) {
+    if (item.length == 0) {
+      return 0;
+    }
+
+    long[] hashLocations = getHashes(item);
+    long res = sketchArray_[(int) hashLocations[0]];
+    for (long h : hashLocations) {
+      res = Math.min(res,  sketchArray_[(int) h]);
+    }
+
+    return res;
+  }
+
+  /**
+   * Returns the upper bound of the estimated frequency for the given item.
+   * @param item The item to estimate.
+   * @return Upper bound of estimated frequency.
+   */
+  public long getUpperBound(final long item) {
+    byte[] longByte = ByteBuffer.allocate(8).putLong(item).array();
+    return getUpperBound(longByte);
+  }
+
+  /**
+   * Returns the upper bound of the estimated frequency for the given item.
+   * @param item The item to estimate.
+   * @return Upper bound of estimated frequency.
+   */
+  public long getUpperBound(final String item) {
+    if (item == null || item.isEmpty()) {
+      return 0;
+    }
+
+    byte[] strByte = item.getBytes(StandardCharsets.UTF_8);
+    return  getUpperBound(strByte);
+  }
+
+  /**
+   * Returns the upper bound of the estimated frequency for the given item.
+   * @param item The item to estimate.
+   * @return Upper bound of estimated frequency.
+   */
+  public long getUpperBound(final byte[] item) {
+    if (item.length == 0) {
+      return 0;
+    }
+
+    return getEstimate(item) + (long)(getRelativeError() * getTotalWeight_());
+  }
+
+  /**
+   * Returns the lower bound of the estimated frequency for the given item.
+   * @param item The item to estimate.
+   * @return Lower bound of estimated frequency.
+   */
+  public long getLowerBound(final long item) {
+    byte[] longByte = ByteBuffer.allocate(8).putLong(item).array();
+    return getLowerBound(longByte);
+  }
+
+  /**
+   * Returns the lower bound of the estimated frequency for the given item.
+   * @param item The item to estimate.
+   * @return Lower bound of estimated frequency.
+   */
+  public long getLowerBound(final String item) {
+    if (item == null || item.isEmpty()) {
+      return 0;
+    }
+
+    byte[] strByte = item.getBytes(StandardCharsets.UTF_8);
+    return getLowerBound(strByte);
+  }
+
+  /**
+   * Returns the lower bound of the estimated frequency for the given item.
+   * @param item The item to estimate.
+   * @return Lower bound of estimated frequency.
+   */
+  public long getLowerBound(final byte[] item) {
+    return getEstimate(item);
+  }
+
+  /**
+   * Merges another CountMinSketch into this one. The sketches must have the same configuration.
+   * @param other The other sketch to merge.
+   */
+  public void merge(final CountMinSketch other) {
+    if (this == other) {
+      throw new SketchesException("Cannot merge a sketch with itself");
+    }
+
+    boolean acceptableConfig = getNumBuckets_() == other.getNumBuckets_() &&
+        getNumHashes_() == other.getNumHashes_() && getSeed_() == other.getSeed_();
+
+    if (!acceptableConfig) {
+      throw new SketchesException("Incompatible sketch configuration.");
+    }
+
+    for (int i = 0; i < sketchArray_.length; i++) {
+      sketchArray_[i] += other.sketchArray_[i];
+    }
+
+    totalWeight_ += other.getTotalWeight_();
+  }
+
+  /**
+   * Serializes the sketch into the provided ByteBuffer.
+   * @param buf The ByteBuffer to write into.
+   */
+  public void serialize(ByteArrayOutputStream buf) {
+    // Long 0
+    final int preambleLongs = Family.COUNTMIN.getMinPreLongs();
+    buf.write((byte) preambleLongs);
+    final int serialVersion = 1;
+    buf.write((byte) serialVersion);
+    final int familyId = Family.COUNTMIN.getID();
+    buf.write((byte) familyId);
+    final int flagsByte = isEmpty() ? Flag.IS_EMPTY.mask() : 0;
+    buf.write((byte)flagsByte);
+    final int NULL_32 = 0;
+    buf.writeBytes(ByteBuffer.allocate(4).putInt(NULL_32).array());
+
+    // Long 1
+    buf.writeBytes(ByteBuffer.allocate(4).putInt(numBuckets_).array());
+    buf.write(numHashes_);
+    short hashSeed = Util.computeSeedHash(seed_);
+    buf.writeBytes(ByteBuffer.allocate(2).putShort(hashSeed).array());
+    final byte NULL_8 = 0;
+    buf.write(NULL_8);
+    if (isEmpty()) {
+      return;
+    }
+
+    final byte[] totWeightByte = ByteBuffer.allocate(8).putLong(totalWeight_).array();
+    buf.writeBytes(totWeightByte);
+
+    for (long w: sketchArray_) {
+      buf.writeBytes(ByteBuffer.allocate(8).putLong(w).array());
+    }
+  }
+
+  /**
+   * Deserializes a CountMinSketch from the provided byte array.
+   * @param b The byte array containing the serialized sketch.
+   * @param seed The seed used during serialization.
+   * @return The deserialized CountMinSketch.
+   */
+  public static CountMinSketch deserialize(final byte[] b, final long seed) {
+    ByteBuffer buf = ByteBuffer.allocate(b.length);
+    buf.put(b);
+    buf.flip();
+
+    final byte preambleLongs = buf.get();
+    final byte serialVersion = buf.get();
+    final byte familyId = buf.get();
+    final byte flagsByte = buf.get();
+    final int NULL_32 = buf.getInt();
+
+    final int numBuckets = buf.getInt();
+    final byte numHashes = buf.get();
+    final short seedHash = buf.getShort();
+    final byte NULL_8 = buf.get();
+
+    if (seedHash != Util.computeSeedHash(seed)) {
+      throw new SketchesArgumentException("Incompatible seed hashes: " + String.valueOf(seedHash) + ", "
+          + String.valueOf(Util.computeSeedHash(seed)));
+    }
+
+    CountMinSketch cms = new CountMinSketch(numHashes, numBuckets, seed);
+    final boolean empty = (flagsByte & Flag.IS_EMPTY.mask()) > 0;
+    if (empty) {
+      return cms;
+    }
+    long w =  buf.getLong();
+    cms.totalWeight_ = w;
+
+    for (int i = 0; i < cms.sketchArray_.length; i++) {
+      cms.sketchArray_[i] = buf.getLong();
+    }
+
+    return cms;
+  }
+}
diff --git a/src/test/java/org/apache/datasketches/count/CountMinSketchTest.java b/src/test/java/org/apache/datasketches/count/CountMinSketchTest.java
new file mode 100644
index 000000000..cbd2fde79
--- /dev/null
+++ b/src/test/java/org/apache/datasketches/count/CountMinSketchTest.java
@@ -0,0 +1,246 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.datasketches.count;
+
+import org.apache.datasketches.common.SketchesArgumentException;
+import org.apache.datasketches.common.SketchesException;
+import org.testng.annotations.Test;
+
+import java.io.ByteArrayOutputStream;
+import java.lang.annotation.Repeatable;
+import java.nio.ByteBuffer;
+
+import static org.testng.Assert.*;
+
+public class CountMinSketchTest {
+  @Test
+  public void createNewCountMinSketchTest() throws Exception {
+    assertThrows(SketchesArgumentException.class, () -> new CountMinSketch((byte) 5, 1, 123));
+    assertThrows(SketchesArgumentException.class, () -> new CountMinSketch((byte) 4, 268435456, 123));
+
+    final byte numHashes = 3;
+    final int numBuckets = 5;
+    final long seed = 1234567;
+    CountMinSketch c = new CountMinSketch(numHashes, numBuckets, seed);
+
+    assertEquals(c.getNumHashes_(), numHashes);
+    assertEquals(c.getNumBuckets_(), numBuckets);
+    assertEquals(c.getSeed_(), seed);
+    assertTrue(c.isEmpty());
+  }
+
+  @Test
+  public void parameterSuggestionsTest() {
+    // Bucket suggestions
+    assertThrows("Relative error must be at least 0.", SketchesException.class, () -> CountMinSketch.suggestNumBuckets(-1.0));
+    assertEquals(CountMinSketch.suggestNumBuckets(0.2), 14);
+    assertEquals(CountMinSketch.suggestNumBuckets(0.1), 28);
+    assertEquals(CountMinSketch.suggestNumBuckets(0.05), 55);
+    assertEquals(CountMinSketch.suggestNumBuckets(0.01), 272);
+
+    // Check that the sketch get_epsilon acts inversely to suggest_num_buckets
+    final byte numHashes = 3;
+    final long seed = 1234567;
+    assertTrue(new CountMinSketch(numHashes, 14, seed).getRelativeError() <= 0.2);
+    assertTrue(new CountMinSketch(numHashes, 28, seed).getRelativeError() <= 0.1);
+    assertTrue(new CountMinSketch(numHashes, 55, seed).getRelativeError() <= 0.05);
+    assertTrue(new CountMinSketch(numHashes, 272, seed).getRelativeError() <= 0.01);
+
+    // Hash suggestions
+    assertThrows("Confidence must be between 0 and 1.0 (inclusive).", SketchesException.class, () -> CountMinSketch.suggestNumHashes(10));
+    assertThrows("Confidence must be between 0 and 1.0 (inclusive).", SketchesException.class, () -> CountMinSketch.suggestNumHashes(-1.0));
+    assertEquals(CountMinSketch.suggestNumHashes(0.682689492), 2);
+    assertEquals(CountMinSketch.suggestNumHashes(0.954499736), 4);
+    assertEquals(CountMinSketch.suggestNumHashes(0.997300204), 6);
+  }
+
+  @Test
+  public void countMinSketchOneUpdateTest() {
+    final byte numHashes = 3;
+    final int numBuckets = 5;
+    final long seed = 1234567;
+    long insertedWeights = 0;
+    CountMinSketch c = new CountMinSketch(numHashes, numBuckets, seed);
+    final String x = "x";
+
+    assertTrue(c.isEmpty());
+    assertEquals(c.getEstimate(x), 0);
+    c.update(x, 1);
+    assertFalse(c.isEmpty());
+    assertEquals(c.getEstimate(x), 1);
+    insertedWeights++;
+
+    final long w = 9;
+    insertedWeights += w;
+    c.update(x, w);
+    assertEquals(c.getEstimate(x), insertedWeights);
+
+    final double w1 = 10.0;
+    insertedWeights += (long) w1;
+    c.update(x, (long) w1);
+    assertEquals(c.getEstimate(x), insertedWeights);
+    assertEquals(c.getTotalWeight_(), insertedWeights);
+    assertTrue(c.getEstimate(x) <= c.getUpperBound(x));
+    assertTrue(c.getEstimate(x) >= c.getLowerBound(x));
+  }
+
+  @Test
+  public void frequencyCancellationTest() {
+    CountMinSketch c = new CountMinSketch((byte) 1, 5, 123456);
+    c.update("x", 1);
+    c.update("y", -1);
+    assertEquals(c.getTotalWeight_(), 2);
+    assertEquals(c.getEstimate("x"), 1);
+    assertEquals(c.getEstimate("y"), -1);
+  }
+
+  @Test
+  public void frequencyEstimates() {
+    final int numItems = 10;
+    long[] data = new long[numItems];
+    long[] frequencies = new long[numItems];
+
+    for (int i = 0; i < numItems; i++) {
+      data[i] = i;
+      frequencies[i] = (long) 1 << (numItems - i);
+    }
+
+    final double relativeError = 0.1;
+    final double confidence = 0.99;
+    final int numBuckets = CountMinSketch.suggestNumBuckets(relativeError);
+    final byte numHashes = CountMinSketch.suggestNumHashes(confidence);
+
+    CountMinSketch c = new CountMinSketch(numHashes, numBuckets, 1234567);
+    for (int i = 0; i < numItems; i++) {
+      final long value = data[i];
+      final long freq = frequencies[i];
+      c.update(value, freq);
+    }
+
+    for (final long i : data) {
+      final long est = c.getEstimate(i);
+      final long upp = c.getUpperBound(i);
+      final long low = c.getLowerBound(i);
+      assertTrue(est <= upp);
+      assertTrue(est >= low);
+    }
+  }
+
+  @Test
+  public void mergeFailTest() {
+    final double relativeError = 0.25;
+    final double confidence = 0.9;
+    final long seed = 1234567;
+    final int numBuckets = CountMinSketch.suggestNumBuckets(relativeError);
+    final byte numHashes = CountMinSketch.suggestNumHashes(confidence);
+    CountMinSketch s = new CountMinSketch(numHashes, numBuckets, seed);
+
+    assertThrows("Cannot merge a sketch with itself.", SketchesException.class, () -> s.merge(s));
+
+    CountMinSketch s1 = new CountMinSketch((byte) (numHashes + 1), numBuckets, seed);
+    CountMinSketch s2 = new CountMinSketch(numHashes, numBuckets + 1, seed);
+    CountMinSketch s3 = new CountMinSketch(numHashes, numBuckets, seed + 1);
+
+    CountMinSketch[] sketches = {s1, s2, s3};
+    for (final CountMinSketch sk : sketches) {
+      assertThrows("Incompatible sketch configuration.", SketchesException.class, () -> s.merge(sk));
+    }
+  }
+
+  @Test
+  public void mergeTest() {
+    final double relativeError = 0.25;
+    final double confidence = 0.9;
+    final long seed = 123456;
+    final int numBuckets = CountMinSketch.suggestNumBuckets(relativeError);
+    final byte numHashes = CountMinSketch.suggestNumHashes(confidence);
+    CountMinSketch c = new CountMinSketch(numHashes, numBuckets, seed);
+
+    final byte sHashes = c.getNumHashes_();
+    final int sBuckets = c.getNumBuckets_();
+    final long sSeed = c.getSeed_();
+    CountMinSketch s = new CountMinSketch(sHashes, sBuckets, sSeed);
+
+    c.merge(s);
+    assertEquals(c.getTotalWeight_(), 0);
+
+    final long[] data = {2, 3, 5, 7};
+    for (final long d : data) {
+      c.update(d, 1);
+      s.update(d, 1);
+    }
+    c.merge(s);
+
+    assertEquals(c.getTotalWeight_(), 2 * s.getTotalWeight_());
+
+    for (final long d : data) {
+      assertTrue(c.getEstimate(d) <= c.getUpperBound(d));
+      assertTrue(s.getEstimate(d) <= 2);
+    }
+  }
+
+  @Test
+  public void serializeDeserializeEmptyTest() {
+    final byte numHashes = 3;
+    final int numBuckets = 32;
+    final long seed = 123456;
+    CountMinSketch c = new CountMinSketch(numHashes, numBuckets, seed);
+
+    ByteArrayOutputStream buf = new ByteArrayOutputStream();
+    c.serialize(buf);
+
+    byte[] b = buf.toByteArray();
+    assertThrows(SketchesArgumentException.class, () -> CountMinSketch.deserialize(b, seed - 1));
+
+    CountMinSketch d = CountMinSketch.deserialize(b, seed);
+    assertEquals(d.getNumHashes_(), c.getNumHashes_());
+    assertEquals(d.getNumBuckets_(), c.getNumBuckets_());
+    assertEquals(d.getSeed_(), c.getSeed_());
+    final long zero = 0;
+    assertEquals(d.getEstimate(zero), c.getEstimate(zero));
+    assertEquals(d.getTotalWeight_(), c.getTotalWeight_());
+  }
+
+  @Test
+  public void serializeDeserializeTest() {
+    final byte numHashes = 5;
+    final int numBuckets = 64;
+    final long seed = 1234456;
+    CountMinSketch c = new CountMinSketch(numHashes, numBuckets, seed);
+    for (long i = 0; i < 10; i++) {
+      c.update(i, 10*i*i);
+    }
+
+    ByteArrayOutputStream buf = new ByteArrayOutputStream();
+    c.serialize(buf);
+
+    assertThrows(SketchesArgumentException.class, () -> CountMinSketch.deserialize(buf.toByteArray(), seed - 1));
+    CountMinSketch d = CountMinSketch.deserialize(buf.toByteArray(), seed);
+
+    assertEquals(d.getNumHashes_(), c.getNumHashes_());
+    assertEquals(d.getNumBuckets_(), c.getNumBuckets_());
+    assertEquals(d.getSeed_(), c.getSeed_());
+    assertEquals(d.getTotalWeight_(), c.getTotalWeight_());
+
+    for (long i = 0; i < 10; i++) {
+      assertEquals(d.getEstimate(i), c.getEstimate(i));
+    }
+  }
+}