diff --git a/Modules/Core/Common/include/itkProcessObject.h b/Modules/Core/Common/include/itkProcessObject.h
index aa5a909a501..930d8dea167 100644
--- a/Modules/Core/Common/include/itkProcessObject.h
+++ b/Modules/Core/Common/include/itkProcessObject.h
@@ -164,8 +164,12 @@ class ITKCommon_EXPORT ProcessObject : public Object
   /** STL array of data object names */
   using NameArray = std::vector<DataObjectIdentifierType>;
 
-  /** Type of general multi-threader interface */
-  using MultiThreaderType = MultiThreaderBase;
+#ifndef ITK_FUTURE_LEGACY_REMOVE
+  /** Type of general multi-threader interface
+   * \deprecated Please use `itk::MultiThreaderBase` directly.
+   */
+  using MultiThreaderType [[deprecated("Please use `itk::MultiThreaderBase` directly.")]] = MultiThreaderBase;
+#endif
 
   /** \brief Return an array with the names of the inputs defined.
    *
@@ -501,7 +505,7 @@ class ITKCommon_EXPORT ProcessObject : public Object
   /** @ITKEndGrouping */
 
   /** Return the multithreader used by this class. */
-  MultiThreaderType *
+  MultiThreaderBase *
   GetMultiThreader() const
   {
     return m_MultiThreader;
@@ -509,7 +513,7 @@ class ITKCommon_EXPORT ProcessObject : public Object
 
   /** Set the multithreader used by this class. */
   void
-  SetMultiThreader(MultiThreaderType * threader);
+  SetMultiThreader(MultiThreaderBase * threader);
 
   /** An opportunity to deallocate a ProcessObject's bulk data
    *  storage. Some filters may wish to reuse existing bulk data
@@ -1002,7 +1006,7 @@ class ITKCommon_EXPORT ProcessObject : public Object
 
   /** Support processing data in multiple threads. Used by subclasses
    * (e.g., ImageSource). */
-  itk::SmartPointer<MultiThreaderType> m_MultiThreader;
+  itk::SmartPointer<MultiThreaderBase> m_MultiThreader;
   ThreadIdType                         m_NumberOfWorkUnits{};
 
   bool m_ThreaderUpdateProgress{ true };
diff --git a/Modules/Core/Common/src/itkProcessObject.cxx b/Modules/Core/Common/src/itkProcessObject.cxx
index d6273a0377d..e0bb50564cd 100644
--- a/Modules/Core/Common/src/itkProcessObject.cxx
+++ b/Modules/Core/Common/src/itkProcessObject.cxx
@@ -63,7 +63,7 @@ ProcessObject::ProcessObject()
   m_IndexedInputs.push_back(m_Inputs.insert(p).first);
   m_IndexedOutputs.push_back(m_Outputs.insert(std::move(p)).first);
 
-  this->Self::SetMultiThreader(MultiThreaderType::New());
+  this->Self::SetMultiThreader(MultiThreaderBase::New());
 }
 
 
@@ -1552,7 +1552,7 @@ ProcessObject::GenerateOutputRequestedRegion(DataObject * output)
 
 
 void
-ProcessObject::SetMultiThreader(MultiThreaderType * threader)
+ProcessObject::SetMultiThreader(MultiThreaderBase * threader)
 {
   if (this->m_MultiThreader != threader)
   {
diff --git a/Modules/Registration/Common/include/itkImageToImageMetric.h b/Modules/Registration/Common/include/itkImageToImageMetric.h
index 4762642ae0b..e7cb4205395 100644
--- a/Modules/Registration/Common/include/itkImageToImageMetric.h
+++ b/Modules/Registration/Common/include/itkImageToImageMetric.h
@@ -349,10 +349,14 @@ class ITK_TEMPLATE_EXPORT ImageToImageMetric : public SingleValuedCostFunction
   itkGetConstReferenceMacro(UseCachingOfBSplineWeights, bool);
   itkBooleanMacro(UseCachingOfBSplineWeights);
   /** @ITKEndGrouping */
-  using MultiThreaderType = MultiThreaderBase;
+
+#ifndef ITK_FUTURE_LEGACY_REMOVE
+  using MultiThreaderType [[deprecated("Please use `itk::MultiThreaderBase` directly.")]] = MultiThreaderBase;
+#endif
+
   /** Get the Threader. */
   /** @ITKStartGrouping */
-  itkGetModifiableObjectMacro(Threader, MultiThreaderType);
+  itkGetModifiableObjectMacro(Threader, MultiThreaderBase);
   const TransformPointer *
   GetThreaderTransform()
   {
@@ -600,7 +604,7 @@ class ITK_TEMPLATE_EXPORT ImageToImageMetric : public SingleValuedCostFunction
   /**
    * \class MultiThreaderWorkUnitInfoImageToImageMetricWrapper
    * This helper local class is used to extract information from the
-   * MultiThreaderType::WorkUnitInfo info type
+   * MultiThreaderBase::WorkUnitInfo info type
    * Do not allow inheritance for objects that are intended for static_cast<void *>
    * \ingroup ITKRegistrationCommon
    */
@@ -608,7 +612,7 @@ class ITK_TEMPLATE_EXPORT ImageToImageMetric : public SingleValuedCostFunction
   {
   public:
     MultiThreaderWorkUnitInfoImageToImageMetricWrapper(const void * workunitInfoAsVoid)
-      : m_WorkUnitInfo(static_cast<const typename MultiThreaderType::WorkUnitInfo *>(workunitInfoAsVoid))
+      : m_WorkUnitInfo(static_cast<const MultiThreaderBase::WorkUnitInfo *>(workunitInfoAsVoid))
     {}
     [[nodiscard]] ThreadIdType
     GetThreadId() const
@@ -622,10 +626,10 @@ class ITK_TEMPLATE_EXPORT ImageToImageMetric : public SingleValuedCostFunction
     }
 
   private:
-    const typename MultiThreaderType::WorkUnitInfo * m_WorkUnitInfo;
+    const MultiThreaderBase::WorkUnitInfo * m_WorkUnitInfo;
   };
 
-  MultiThreaderType::Pointer              m_Threader{};
+  MultiThreaderBase::Pointer              m_Threader{};
   std::unique_ptr<ConstantPointerWrapper> m_ConstSelfWrapper;
   mutable std::unique_ptr<unsigned int[]> m_ThreaderNumberOfMovingImageSamples;
   bool                                    m_WithinThreadPreProcess{ false };
diff --git a/Modules/Registration/Common/include/itkImageToImageMetric.hxx b/Modules/Registration/Common/include/itkImageToImageMetric.hxx
index 342dc807519..84546dec784 100644
--- a/Modules/Registration/Common/include/itkImageToImageMetric.hxx
+++ b/Modules/Registration/Common/include/itkImageToImageMetric.hxx
@@ -54,7 +54,7 @@ ImageToImageMetric<TFixedImage, TMovingImage>::ImageToImageMetric()
   , m_BSplineTransformIndices()
   , m_BSplineInterpolator(nullptr)
   , m_DerivativeCalculator(nullptr)
-  , m_Threader(MultiThreaderType::New())
+  , m_Threader(MultiThreaderBase::New())
   , m_ConstSelfWrapper(std::make_unique<ConstantPointerWrapper>(this))
 {
   this->m_NumberOfWorkUnits = this->m_Threader->GetNumberOfWorkUnits();