diff --git a/mlir/CMakeLists.txt b/mlir/CMakeLists.txt
--- a/mlir/CMakeLists.txt
+++ b/mlir/CMakeLists.txt
@@ -96,6 +96,8 @@
     not desired. Enabling this will result in object files being written \
     under lib/objects-{CMAKE_BUILD_TYPE}.")
 
+set(MLIR_BUILD_MLIR_C_DYLIB 0 CACHE BOOL "Builds libMLIR-C shared library.")
+
 #-------------------------------------------------------------------------------
 # Python Bindings Configuration
 # Requires:
diff --git a/mlir/include/mlir/ExecutionEngine/CRunnerUtils.h b/mlir/include/mlir/ExecutionEngine/CRunnerUtils.h
--- a/mlir/include/mlir/ExecutionEngine/CRunnerUtils.h
+++ b/mlir/include/mlir/ExecutionEngine/CRunnerUtils.h
@@ -27,7 +27,8 @@
 #endif // mlir_c_runner_utils_EXPORTS
 #endif // MLIR_CRUNNERUTILS_EXPORT
 #else  // _WIN32
-#define MLIR_CRUNNERUTILS_EXPORT
+// Non-windows: use visibility attributes.
+#define MLIR_CRUNNERUTILS_EXPORT __attribute__((visibility("default")))
 #define MLIR_CRUNNERUTILS_DEFINE_FUNCTIONS
 #endif // _WIN32
 
diff --git a/mlir/include/mlir/ExecutionEngine/RunnerUtils.h b/mlir/include/mlir/ExecutionEngine/RunnerUtils.h
--- a/mlir/include/mlir/ExecutionEngine/RunnerUtils.h
+++ b/mlir/include/mlir/ExecutionEngine/RunnerUtils.h
@@ -27,7 +27,8 @@
 #endif // mlir_runner_utils_EXPORTS
 #endif // MLIR_RUNNERUTILS_EXPORT
 #else
-#define MLIR_RUNNERUTILS_EXPORT
+// Non-windows: use visibility attributes.
+#define MLIR_RUNNERUTILS_EXPORT __attribute__((visibility("default")))
 #endif // _WIN32
 
 #include <assert.h>
diff --git a/mlir/lib/CAPI/CMakeLists.txt b/mlir/lib/CAPI/CMakeLists.txt
--- a/mlir/lib/CAPI/CMakeLists.txt
+++ b/mlir/lib/CAPI/CMakeLists.txt
@@ -1,3 +1,12 @@
+# For upstream, we accumulate all libraries into the MLIR_CAPI_LIBRARIES
+# property via a custom wrapper function. This is then used to create an
+# aggregate below.
+set_property(GLOBAL APPEND PROPERTY MLIR_CAPI_LIBRARIES)
+function(add_mlir_upstream_c_api_library name)
+  add_mlir_public_c_api_library(${name} ${ARGN})
+  set_property(GLOBAL APPEND PROPERTY MLIR_CAPI_LIBRARIES ${name})
+endfunction()
+
 add_subdirectory(Debug)
 add_subdirectory(Dialect)
 add_subdirectory(Conversion)
@@ -6,3 +15,21 @@
 add_subdirectory(IR)
 add_subdirectory(Registration)
 add_subdirectory(Transforms)
+
+# Build the optional CAPI dylib.
+if(MLIR_BUILD_MLIR_C_DYLIB)
+  message(STATUS "Building MLIR-C dylib")
+  get_property(_capi_libraries GLOBAL PROPERTY MLIR_CAPI_LIBRARIES)
+  add_mlir_aggregate(MLIR-C
+    SHARED
+    EMBED_LIBS
+      ${_capi_libraries}
+  )
+  if(CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    target_link_options(MLIR-C PRIVATE "-Wl,-exclude-libs,ALL")
+  else()
+    if(NOT CMAKE_C_VISIBILITY_PRESET STREQUAL "hidden" OR NOT CMAKE_CXX_VISIBILITY_PRESET STREQUAL "hidden")
+      message(STATUS "MLIR-C on this platform exports all symbols. Recommend building with CMAKE_(C|CXX)_VISIBILITY_PRESET=hidden or implement filtering support.")
+    endif()
+  endif()
+endif()
diff --git a/mlir/lib/CAPI/Conversion/CMakeLists.txt b/mlir/lib/CAPI/Conversion/CMakeLists.txt
--- a/mlir/lib/CAPI/Conversion/CMakeLists.txt
+++ b/mlir/lib/CAPI/Conversion/CMakeLists.txt
@@ -1,5 +1,5 @@
 get_property(conversion_libs GLOBAL PROPERTY MLIR_CONVERSION_LIBS)
-add_mlir_public_c_api_library(MLIRCAPIConversion
+add_mlir_upstream_c_api_library(MLIRCAPIConversion
   Passes.cpp
 
   LINK_LIBS PUBLIC
diff --git a/mlir/lib/CAPI/Debug/CMakeLists.txt b/mlir/lib/CAPI/Debug/CMakeLists.txt
--- a/mlir/lib/CAPI/Debug/CMakeLists.txt
+++ b/mlir/lib/CAPI/Debug/CMakeLists.txt
@@ -1,4 +1,4 @@
-add_mlir_public_c_api_library(MLIRCAPIDebug
+add_mlir_upstream_c_api_library(MLIRCAPIDebug
   Debug.cpp
 
   LINK_LIBS PUBLIC
diff --git a/mlir/lib/CAPI/Dialect/CMakeLists.txt b/mlir/lib/CAPI/Dialect/CMakeLists.txt
--- a/mlir/lib/CAPI/Dialect/CMakeLists.txt
+++ b/mlir/lib/CAPI/Dialect/CMakeLists.txt
@@ -1,4 +1,4 @@
-add_mlir_public_c_api_library(MLIRCAPIAsync
+add_mlir_upstream_c_api_library(MLIRCAPIAsync
   Async.cpp
   AsyncPasses.cpp
 
@@ -13,7 +13,7 @@
   MLIRPass
 )
 
-add_mlir_public_c_api_library(MLIRCAPIGPU
+add_mlir_upstream_c_api_library(MLIRCAPIGPU
   GPU.cpp
   GPUPasses.cpp
 
@@ -27,7 +27,7 @@
   MLIRPass
 )
 
-add_mlir_public_c_api_library(MLIRCAPILLVM
+add_mlir_upstream_c_api_library(MLIRCAPILLVM
   LLVM.cpp
 
   PARTIAL_SOURCES_INTENDED
@@ -36,7 +36,7 @@
   MLIRLLVMIR
 )
 
-add_mlir_public_c_api_library(MLIRCAPILinalg
+add_mlir_upstream_c_api_library(MLIRCAPILinalg
   Linalg.cpp
   LinalgPasses.cpp
 
@@ -51,7 +51,7 @@
   MLIRLinalgTransforms
 )
 
-add_mlir_public_c_api_library(MLIRCAPISCF
+add_mlir_upstream_c_api_library(MLIRCAPISCF
   SCF.cpp
 
   PARTIAL_SOURCES_INTENDED
@@ -60,7 +60,7 @@
   MLIRSCF
 )
 
-add_mlir_public_c_api_library(MLIRCAPIShape
+add_mlir_upstream_c_api_library(MLIRCAPIShape
   Shape.cpp
 
   PARTIAL_SOURCES_INTENDED
@@ -69,7 +69,7 @@
   MLIRShape
 )
 
-add_mlir_public_c_api_library(MLIRCAPISparseTensor
+add_mlir_upstream_c_api_library(MLIRCAPISparseTensor
   SparseTensor.cpp
   SparseTensorPasses.cpp
 
@@ -80,7 +80,7 @@
   MLIRSparseTensorTransforms
 )
 
-add_mlir_public_c_api_library(MLIRCAPIStandard
+add_mlir_upstream_c_api_library(MLIRCAPIStandard
   Standard.cpp
 
   PARTIAL_SOURCES_INTENDED
@@ -89,7 +89,7 @@
   MLIRStandard
 )
 
-add_mlir_public_c_api_library(MLIRCAPITensor
+add_mlir_upstream_c_api_library(MLIRCAPITensor
   Tensor.cpp
 
   PARTIAL_SOURCES_INTENDED
diff --git a/mlir/lib/CAPI/ExecutionEngine/CMakeLists.txt b/mlir/lib/CAPI/ExecutionEngine/CMakeLists.txt
--- a/mlir/lib/CAPI/ExecutionEngine/CMakeLists.txt
+++ b/mlir/lib/CAPI/ExecutionEngine/CMakeLists.txt
@@ -1,5 +1,5 @@
 # Main API shared library.
-add_mlir_public_c_api_library(MLIRCEXECUTIONENGINE
+add_mlir_upstream_c_api_library(MLIRCEXECUTIONENGINE
   ExecutionEngine.cpp
 
   LINK_LIBS PUBLIC
diff --git a/mlir/lib/CAPI/IR/CMakeLists.txt b/mlir/lib/CAPI/IR/CMakeLists.txt
--- a/mlir/lib/CAPI/IR/CMakeLists.txt
+++ b/mlir/lib/CAPI/IR/CMakeLists.txt
@@ -1,5 +1,5 @@
 # Main API shared library.
-add_mlir_public_c_api_library(MLIRCAPIIR
+add_mlir_upstream_c_api_library(MLIRCAPIIR
   AffineExpr.cpp
   AffineMap.cpp
   BuiltinAttributes.cpp
diff --git a/mlir/lib/CAPI/Interfaces/CMakeLists.txt b/mlir/lib/CAPI/Interfaces/CMakeLists.txt
--- a/mlir/lib/CAPI/Interfaces/CMakeLists.txt
+++ b/mlir/lib/CAPI/Interfaces/CMakeLists.txt
@@ -1,4 +1,4 @@
-add_mlir_public_c_api_library(MLIRCAPIInterfaces
+add_mlir_upstream_c_api_library(MLIRCAPIInterfaces
   Interfaces.cpp
 
   LINK_LIBS PUBLIC
diff --git a/mlir/lib/CAPI/Registration/CMakeLists.txt b/mlir/lib/CAPI/Registration/CMakeLists.txt
--- a/mlir/lib/CAPI/Registration/CMakeLists.txt
+++ b/mlir/lib/CAPI/Registration/CMakeLists.txt
@@ -2,7 +2,7 @@
 get_property(dialect_libs GLOBAL PROPERTY MLIR_DIALECT_LIBS)
 get_property(translation_libs GLOBAL PROPERTY MLIR_TRANSLATION_LIBS)
 get_property(conversion_libs GLOBAL PROPERTY MLIR_CONVERSION_LIBS)
-add_mlir_public_c_api_library(MLIRCAPIRegistration
+add_mlir_upstream_c_api_library(MLIRCAPIRegistration
   Registration.cpp
 
   LINK_LIBS PUBLIC
diff --git a/mlir/lib/CAPI/Transforms/CMakeLists.txt b/mlir/lib/CAPI/Transforms/CMakeLists.txt
--- a/mlir/lib/CAPI/Transforms/CMakeLists.txt
+++ b/mlir/lib/CAPI/Transforms/CMakeLists.txt
@@ -1,4 +1,4 @@
-add_mlir_public_c_api_library(MLIRCAPITransforms
+add_mlir_upstream_c_api_library(MLIRCAPITransforms
   Passes.cpp
 
   LINK_LIBS PUBLIC
diff --git a/mlir/test/CAPI/CMakeLists.txt b/mlir/test/CAPI/CMakeLists.txt
--- a/mlir/test/CAPI/CMakeLists.txt
+++ b/mlir/test/CAPI/CMakeLists.txt
@@ -10,8 +10,13 @@
     PARTIAL_SOURCES_INTENDED
     ${ARG_UNPARSED_ARGUMENTS})
   llvm_update_compile_flags(${name})
-  target_link_libraries(${name}
-    ${ARG_LINK_LIBS})
+  if(MLIR_BUILD_MLIR_C_DYLIB)
+    target_link_libraries(${name} PRIVATE
+      MLIR-C)
+  else()
+    target_link_libraries(${name} PRIVATE
+      ${ARG_LINK_LIBS})
+  endif()
 endfunction(_add_capi_test_executable)
 
 _add_capi_test_executable(mlir-capi-execution-engine-test