diff --git a/clang/docs/tools/clang-formatted-files.txt b/clang/docs/tools/clang-formatted-files.txt
--- a/clang/docs/tools/clang-formatted-files.txt
+++ b/clang/docs/tools/clang-formatted-files.txt
@@ -5707,7 +5707,6 @@
 llvm/include/llvm-c/Error.h
 llvm/include/llvm-c/ErrorHandling.h
 llvm/include/llvm-c/ExternC.h
-llvm/include/llvm-c/Initialization.h
 llvm/include/llvm-c/IRReader.h
 llvm/include/llvm-c/LLJIT.h
 llvm/include/llvm-c/OrcEE.h
diff --git a/llvm/bindings/python/llvm/core.py b/llvm/bindings/python/llvm/core.py
--- a/llvm/bindings/python/llvm/core.py
+++ b/llvm/bindings/python/llvm/core.py
@@ -31,7 +31,6 @@
     "BasicBlock",
     "Instruction",
     "Context",
-    "PassRegistry"
 ]
 
 lib = get_library()
@@ -440,49 +439,11 @@
     def GetGlobalContext(cls):
         return Context(lib.LLVMGetGlobalContext())
 
-class PassRegistry(LLVMObject):
-    """Represents an opaque pass registry object."""
-
-    def __init__(self):
-        LLVMObject.__init__(self,
-                            lib.LLVMGetGlobalPassRegistry())
-
 def register_library(library):
     # Initialization/Shutdown declarations.
-    library.LLVMInitializeCore.argtypes = [PassRegistry]
-    library.LLVMInitializeCore.restype = None
-
-    library.LLVMInitializeTransformUtils.argtypes = [PassRegistry]
-    library.LLVMInitializeTransformUtils.restype = None
-
-    library.LLVMInitializeScalarOpts.argtypes = [PassRegistry]
-    library.LLVMInitializeScalarOpts.restype = None
-
-    library.LLVMInitializeVectorization.argtypes = [PassRegistry]
-    library.LLVMInitializeVectorization.restype = None
-
-    library.LLVMInitializeInstCombine.argtypes = [PassRegistry]
-    library.LLVMInitializeInstCombine.restype = None
-
-    library.LLVMInitializeIPO.argtypes = [PassRegistry]
-    library.LLVMInitializeIPO.restype = None
-
-    library.LLVMInitializeAnalysis.argtypes = [PassRegistry]
-    library.LLVMInitializeAnalysis.restype = None
-
-    library.LLVMInitializeCodeGen.argtypes = [PassRegistry]
-    library.LLVMInitializeCodeGen.restype = None
-
-    library.LLVMInitializeTarget.argtypes = [PassRegistry]
-    library.LLVMInitializeTarget.restype = None
-
     library.LLVMShutdown.argtypes = []
     library.LLVMShutdown.restype = None
 
-    # Pass Registry declarations.
-    library.LLVMGetGlobalPassRegistry.argtypes = []
-    library.LLVMGetGlobalPassRegistry.restype = c_object_p
-
     # Context declarations.
     library.LLVMContextCreate.argtypes = []
     library.LLVMContextCreate.restype = c_object_p
@@ -613,16 +574,6 @@
 
 def initialize_llvm():
     Context.GetGlobalContext()
-    p = PassRegistry()
-    lib.LLVMInitializeCore(p)
-    lib.LLVMInitializeTransformUtils(p)
-    lib.LLVMInitializeScalarOpts(p)
-    lib.LLVMInitializeVectorization(p)
-    lib.LLVMInitializeInstCombine(p)
-    lib.LLVMInitializeIPO(p)
-    lib.LLVMInitializeAnalysis(p)
-    lib.LLVMInitializeCodeGen(p)
-    lib.LLVMInitializeTarget(p)
 
 register_library(lib)
 Enums = register_enumerations()
diff --git a/llvm/docs/ReleaseNotes.rst b/llvm/docs/ReleaseNotes.rst
--- a/llvm/docs/ReleaseNotes.rst
+++ b/llvm/docs/ReleaseNotes.rst
@@ -191,6 +191,11 @@
   have been removed.
 * Removed ``LLVMPassManagerBuilderRef`` and functions interacting with it.
   These belonged to the no longer supported legacy pass manager.
+* Functions for initializing legacy passes like ``LLVMInitializeInstCombine``
+  have been removed. Calls to such functions can simply be dropped, as they are
+  no longer necessary.
+* ``LLVMPassRegistryRef`` and ``LLVMGetGlobalPassRegistry``, which were only
+  useful in conjunction with initialization functions, have been removed.
 * As part of the opaque pointer transition, ``LLVMGetElementType`` no longer
   gives the pointee type of a pointer type.
 * The following functions for creating constant expressions have been removed,
diff --git a/llvm/include/llvm-c/Core.h b/llvm/include/llvm-c/Core.h
--- a/llvm/include/llvm-c/Core.h
+++ b/llvm/include/llvm-c/Core.h
@@ -474,8 +474,6 @@
  * @}
  */
 
-void LLVMInitializeCore(LLVMPassRegistryRef R);
-
 /** Deallocate and destroy all ManagedStatic variables.
     @see llvm::llvm_shutdown
     @see ManagedStatic */
@@ -4158,21 +4156,6 @@
 size_t LLVMGetBufferSize(LLVMMemoryBufferRef MemBuf);
 void LLVMDisposeMemoryBuffer(LLVMMemoryBufferRef MemBuf);
 
-/**
- * @}
- */
-
-/**
- * @defgroup LLVMCCorePassRegistry Pass Registry
- * @ingroup LLVMCCore
- *
- * @{
- */
-
-/** Return the global pass registry, for use with initialization functions.
-    @see llvm::PassRegistry::getPassRegistry */
-LLVMPassRegistryRef LLVMGetGlobalPassRegistry(void);
-
 /**
  * @}
  */
diff --git a/llvm/include/llvm-c/Initialization.h b/llvm/include/llvm-c/Initialization.h
deleted file mode 100644
--- a/llvm/include/llvm-c/Initialization.h
+++ /dev/null
@@ -1,50 +0,0 @@
-/*===-- llvm-c/Initialization.h - Initialization C Interface ------*- C -*-===*\
-|*                                                                            *|
-|* Part of the LLVM Project, under the Apache License v2.0 with LLVM          *|
-|* Exceptions.                                                                *|
-|* See https://llvm.org/LICENSE.txt for license information.                  *|
-|* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception                    *|
-|*                                                                            *|
-|*===----------------------------------------------------------------------===*|
-|*                                                                            *|
-|* This header declares the C interface to LLVM initialization routines,      *|
-|* which must be called before you can use the functionality provided by      *|
-|* the corresponding LLVM library.                                            *|
-|*                                                                            *|
-\*===----------------------------------------------------------------------===*/
-
-#ifndef LLVM_C_INITIALIZATION_H
-#define LLVM_C_INITIALIZATION_H
-
-#include "llvm-c/ExternC.h"
-#include "llvm-c/Types.h"
-
-LLVM_C_EXTERN_C_BEGIN
-
-/**
- * @defgroup LLVMCInitialization Initialization Routines
- * @ingroup LLVMC
- *
- * This module contains routines used to initialize the LLVM system.
- *
- * @{
- */
-
-void LLVMInitializeCore(LLVMPassRegistryRef R);
-void LLVMInitializeTransformUtils(LLVMPassRegistryRef R);
-void LLVMInitializeScalarOpts(LLVMPassRegistryRef R);
-void LLVMInitializeVectorization(LLVMPassRegistryRef R);
-void LLVMInitializeInstCombine(LLVMPassRegistryRef R);
-void LLVMInitializeIPO(LLVMPassRegistryRef R);
-void LLVMInitializeAnalysis(LLVMPassRegistryRef R);
-void LLVMInitializeIPA(LLVMPassRegistryRef R);
-void LLVMInitializeCodeGen(LLVMPassRegistryRef R);
-void LLVMInitializeTarget(LLVMPassRegistryRef R);
-
-/**
- * @}
- */
-
-LLVM_C_EXTERN_C_END
-
-#endif
diff --git a/llvm/include/llvm-c/Types.h b/llvm/include/llvm-c/Types.h
--- a/llvm/include/llvm-c/Types.h
+++ b/llvm/include/llvm-c/Types.h
@@ -126,9 +126,6 @@
 /** @see llvm::PassManagerBase */
 typedef struct LLVMOpaquePassManager *LLVMPassManagerRef;
 
-/** @see llvm::PassRegistry */
-typedef struct LLVMOpaquePassRegistry *LLVMPassRegistryRef;
-
 /**
  * Used to get the users and usees of a Value.
  *
diff --git a/llvm/include/llvm/PassRegistry.h b/llvm/include/llvm/PassRegistry.h
--- a/llvm/include/llvm/PassRegistry.h
+++ b/llvm/include/llvm/PassRegistry.h
@@ -19,7 +19,6 @@
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/StringRef.h"
-#include "llvm/Support/CBindingWrapping.h"
 #include "llvm/Support/RWMutex.h"
 #include <memory>
 #include <vector>
@@ -89,9 +88,6 @@
   void removeRegistrationListener(PassRegistrationListener *L);
 };
 
-// Create wrappers for C Binding types (see CBindingWrapping.h).
-DEFINE_STDCXX_CONVERSION_FUNCTIONS(PassRegistry, LLVMPassRegistryRef)
-
 } // end namespace llvm
 
 #endif // LLVM_PASSREGISTRY_H
diff --git a/llvm/lib/Analysis/Analysis.cpp b/llvm/lib/Analysis/Analysis.cpp
--- a/llvm/lib/Analysis/Analysis.cpp
+++ b/llvm/lib/Analysis/Analysis.cpp
@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm-c/Analysis.h"
-#include "llvm-c/Initialization.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Verifier.h"
 #include "llvm/InitializePasses.h"
@@ -85,14 +84,6 @@
   initializeMemorySSAPrinterLegacyPassPass(Registry);
 }
 
-void LLVMInitializeAnalysis(LLVMPassRegistryRef R) {
-  initializeAnalysis(*unwrap(R));
-}
-
-void LLVMInitializeIPA(LLVMPassRegistryRef R) {
-  initializeAnalysis(*unwrap(R));
-}
-
 LLVMBool LLVMVerifyModule(LLVMModuleRef M, LLVMVerifierFailureAction Action,
                           char **OutMessages) {
   raw_ostream *DebugOS = Action != LLVMReturnStatusAction ? &errs() : nullptr;
diff --git a/llvm/lib/CodeGen/CodeGen.cpp b/llvm/lib/CodeGen/CodeGen.cpp
--- a/llvm/lib/CodeGen/CodeGen.cpp
+++ b/llvm/lib/CodeGen/CodeGen.cpp
@@ -11,7 +11,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm-c/Initialization.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/PassRegistry.h"
 
@@ -141,7 +140,3 @@
   initializeWinEHPreparePass(Registry);
   initializeXRayInstrumentationPass(Registry);
 }
-
-void LLVMInitializeCodeGen(LLVMPassRegistryRef R) {
-  initializeCodeGen(*unwrap(R));
-}
diff --git a/llvm/lib/IR/Core.cpp b/llvm/lib/IR/Core.cpp
--- a/llvm/lib/IR/Core.cpp
+++ b/llvm/lib/IR/Core.cpp
@@ -53,10 +53,6 @@
   initializeVerifierLegacyPassPass(Registry);
 }
 
-void LLVMInitializeCore(LLVMPassRegistryRef R) {
-  initializeCore(*unwrap(R));
-}
-
 void LLVMShutdown() {
   llvm_shutdown();
 }
@@ -4071,12 +4067,6 @@
   delete unwrap(MemBuf);
 }
 
-/*===-- Pass Registry -----------------------------------------------------===*/
-
-LLVMPassRegistryRef LLVMGetGlobalPassRegistry(void) {
-  return wrap(PassRegistry::getPassRegistry());
-}
-
 /*===-- Pass Manager ------------------------------------------------------===*/
 
 LLVMPassManagerRef LLVMCreatePassManager() {
diff --git a/llvm/lib/Target/Target.cpp b/llvm/lib/Target/Target.cpp
--- a/llvm/lib/Target/Target.cpp
+++ b/llvm/lib/Target/Target.cpp
@@ -12,7 +12,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm-c/Target.h"
-#include "llvm-c/Initialization.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/LLVMContext.h"
@@ -40,10 +39,6 @@
   initializeTargetTransformInfoWrapperPassPass(Registry);
 }
 
-void LLVMInitializeTarget(LLVMPassRegistryRef R) {
-  initializeTarget(*unwrap(R));
-}
-
 LLVMTargetDataRef LLVMGetModuleDataLayout(LLVMModuleRef M) {
   return wrap(&unwrap(M)->getDataLayout());
 }
diff --git a/llvm/lib/Transforms/IPO/IPO.cpp b/llvm/lib/Transforms/IPO/IPO.cpp
--- a/llvm/lib/Transforms/IPO/IPO.cpp
+++ b/llvm/lib/Transforms/IPO/IPO.cpp
@@ -12,7 +12,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "llvm-c/Initialization.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Transforms/IPO.h"
 #include "llvm/Transforms/IPO/AlwaysInliner.h"
@@ -28,7 +27,3 @@
   initializeSingleLoopExtractorPass(Registry);
   initializeBarrierNoopPass(Registry);
 }
-
-void LLVMInitializeIPO(LLVMPassRegistryRef R) {
-  initializeIPO(*unwrap(R));
-}
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -33,7 +33,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "InstCombineInternal.h"
-#include "llvm-c/Initialization.h"
 #include "llvm/ADT/APInt.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/DenseMap.h"
@@ -4401,10 +4400,6 @@
   initializeInstructionCombiningPassPass(Registry);
 }
 
-void LLVMInitializeInstCombine(LLVMPassRegistryRef R) {
-  initializeInstructionCombiningPassPass(*unwrap(R));
-}
-
 FunctionPass *llvm::createInstructionCombiningPass() {
   return new InstructionCombiningPass();
 }
diff --git a/llvm/lib/Transforms/Instrumentation/Instrumentation.cpp b/llvm/lib/Transforms/Instrumentation/Instrumentation.cpp
--- a/llvm/lib/Transforms/Instrumentation/Instrumentation.cpp
+++ b/llvm/lib/Transforms/Instrumentation/Instrumentation.cpp
@@ -12,11 +12,8 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Instrumentation.h"
-#include "llvm-c/Initialization.h"
 #include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Module.h"
-#include "llvm/InitializePasses.h"
-#include "llvm/PassRegistry.h"
 #include "llvm/TargetParser/Triple.h"
 
 using namespace llvm;
diff --git a/llvm/lib/Transforms/Scalar/Scalar.cpp b/llvm/lib/Transforms/Scalar/Scalar.cpp
--- a/llvm/lib/Transforms/Scalar/Scalar.cpp
+++ b/llvm/lib/Transforms/Scalar/Scalar.cpp
@@ -13,7 +13,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Scalar.h"
-#include "llvm-c/Initialization.h"
 #include "llvm/Analysis/BasicAliasAnalysis.h"
 #include "llvm/Analysis/ScopedNoAliasAA.h"
 #include "llvm/Analysis/TypeBasedAliasAnalysis.h"
@@ -83,7 +82,3 @@
   initializePlaceSafepointsLegacyPassPass(Registry);
   initializeLoopSimplifyCFGLegacyPassPass(Registry);
 }
-
-void LLVMInitializeScalarOpts(LLVMPassRegistryRef R) {
-  initializeScalarOpts(*unwrap(R));
-}
diff --git a/llvm/lib/Transforms/Utils/Utils.cpp b/llvm/lib/Transforms/Utils/Utils.cpp
--- a/llvm/lib/Transforms/Utils/Utils.cpp
+++ b/llvm/lib/Transforms/Utils/Utils.cpp
@@ -12,7 +12,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Utils.h"
-#include "llvm-c/Initialization.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/Pass.h"
 #include "llvm/PassRegistry.h"
@@ -42,8 +41,3 @@
   initializeFixIrreduciblePass(Registry);
   initializeUnifyLoopExitsLegacyPassPass(Registry);
 }
-
-/// LLVMInitializeTransformUtils - C binding for initializeTransformUtilsPasses.
-void LLVMInitializeTransformUtils(LLVMPassRegistryRef R) {
-  initializeTransformUtils(*unwrap(R));
-}
diff --git a/llvm/lib/Transforms/Vectorize/Vectorize.cpp b/llvm/lib/Transforms/Vectorize/Vectorize.cpp
--- a/llvm/lib/Transforms/Vectorize/Vectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/Vectorize.cpp
@@ -13,7 +13,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Vectorize.h"
-#include "llvm-c/Initialization.h"
 #include "llvm/InitializePasses.h"
 #include "llvm/PassRegistry.h"
 
@@ -23,7 +22,3 @@
 void llvm::initializeVectorization(PassRegistry &Registry) {
   initializeLoadStoreVectorizerLegacyPassPass(Registry);
 }
-
-void LLVMInitializeVectorization(LLVMPassRegistryRef R) {
-  initializeVectorization(*unwrap(R));
-}
diff --git a/llvm/tools/llvm-c-test/include-all.c b/llvm/tools/llvm-c-test/include-all.c
--- a/llvm/tools/llvm-c-test/include-all.c
+++ b/llvm/tools/llvm-c-test/include-all.c
@@ -26,7 +26,6 @@
 #include "llvm-c/Error.h"
 #include "llvm-c/ErrorHandling.h"
 #include "llvm-c/ExecutionEngine.h"
-#include "llvm-c/Initialization.h"
 #include "llvm-c/IRReader.h"
 #include "llvm-c/Linker.h"
 #include "llvm-c/Object.h"
diff --git a/llvm/tools/llvm-c-test/main.c b/llvm/tools/llvm-c-test/main.c
--- a/llvm/tools/llvm-c-test/main.c
+++ b/llvm/tools/llvm-c-test/main.c
@@ -68,10 +68,6 @@
 }
 
 int main(int argc, char **argv) {
-  LLVMPassRegistryRef pr = LLVMGetGlobalPassRegistry();
-
-  LLVMInitializeCore(pr);
-
   if (argc == 2 && !strcmp(argv[1], "--lazy-new-module-dump")) {
     return llvm_module_dump(true, true);
   } else if (argc == 2 && !strcmp(argv[1], "--new-module-dump")) {