diff --git a/NEWS.md b/NEWS.md
index 1b9f87c09b..afcfb374fc 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -35,13 +35,6 @@ Note: We're only listing outstanding class updates.
       The class use equality semantic to lookup keys like a regular hash,
       but it doesn't hold strong references on the keys. [[Feature #18498]]
 
-* Process.warnup
-
-    * Notify the Ruby virtual machine that the boot sequence is finished,
-      and that now is a good time to optimize the application. This is useful
-      for long running applications. The actual optimizations performed are entirely
-      implementation specific and may change in the future without notice. [[Feature #18885]
-
 ## Stdlib updates
 
 The following default gems are updated.
diff --git a/common.mk b/common.mk
index e186b06d73..b1cf9b05a2 100644
--- a/common.mk
+++ b/common.mk
@@ -11024,9 +11024,7 @@ process.$(OBJEXT): {$(VPATH)}thread_$(THREAD_MODEL).h
 process.$(OBJEXT): {$(VPATH)}thread_native.h
 process.$(OBJEXT): {$(VPATH)}util.h
 process.$(OBJEXT): {$(VPATH)}vm_core.h
-process.$(OBJEXT): {$(VPATH)}vm_debug.h
 process.$(OBJEXT): {$(VPATH)}vm_opts.h
-process.$(OBJEXT): {$(VPATH)}vm_sync.h
 ractor.$(OBJEXT): $(CCAN_DIR)/check_type/check_type.h
 ractor.$(OBJEXT): $(CCAN_DIR)/container_of/container_of.h
 ractor.$(OBJEXT): $(CCAN_DIR)/list/list.h
diff --git a/gc.c b/gc.c
index 4050c47edf..3dc63433a7 100644
--- a/gc.c
+++ b/gc.c
@@ -9833,26 +9833,6 @@ garbage_collect_with_gvl(rb_objspace_t *objspace, unsigned int reason)
     }
 }
 
-static int
-gc_promote_object_i(void *vstart, void *vend, size_t stride, void *data)
-{
-    rb_objspace_t *objspace = &rb_objspace;
-    VALUE v = (VALUE)vstart;
-    for (; v != (VALUE)vend; v += stride) {
-        switch (BUILTIN_TYPE(v)) {
-          case T_NONE:
-          case T_ZOMBIE:
-            break;
-          default:
-            if (!RVALUE_OLD_P(v) && !RVALUE_WB_UNPROTECTED(v)) {
-                RVALUE_AGE_SET_OLD(objspace, v);
-            }
-        }
-    }
-
-    return 0;
-}
-
 static VALUE
 gc_start_internal(rb_execution_context_t *ec, VALUE self, VALUE full_mark, VALUE immediate_mark, VALUE immediate_sweep, VALUE compact)
 {
@@ -9880,33 +9860,6 @@ gc_start_internal(rb_execution_context_t *ec, VALUE self, VALUE full_mark, VALUE
     return Qnil;
 }
 
-void
-rb_gc_prepare_heap(void)
-{
-    gc_start_internal(NULL, Qtrue, Qtrue, Qtrue, Qtrue, Qtrue);
-
-    /* Flush any postponed jobs.
-     * Transient heap uses postponed jobs to mark things, so we need to
-     * give it a chance to finish what it was doing. */
-    rb_postponed_job_flush(GET_VM());
-
-    /* The transient heap need to be evacuated before we promote objects.
-     * First put the transient heap in marking mode so that we can 
-     * evacuate everything.  Then evacuate everything. Then finish up
-     * marking mode so that the transient heap is in the right mode
-     * for the next GC. */
-    rb_transient_heap_start_marking(true);
-    rb_transient_heap_evacuate();
-    rb_transient_heap_finish_marking();
-
-    /* Finally, promote everyone to old gen, but don't let the GC run
-     * while we iterate over the heap. */
-    VALUE gc_disabled = rb_gc_disable_no_rest();
-    rb_objspace_each_objects(gc_promote_object_i, NULL);
-    if (gc_disabled != Qtrue) rb_gc_enable();
-    rb_transient_heap_verify();
-}
-
 static int
 gc_is_moveable_obj(rb_objspace_t *objspace, VALUE obj)
 {
diff --git a/internal/gc.h b/internal/gc.h
index e0cc3bfa8a..2b67ca40dc 100644
--- a/internal/gc.h
+++ b/internal/gc.h
@@ -214,7 +214,6 @@ extern VALUE *ruby_initial_gc_stress_ptr;
 extern int ruby_disable_gc;
 RUBY_ATTR_MALLOC void *ruby_mimmalloc(size_t size);
 void ruby_mimfree(void *ptr);
-void rb_gc_prepare_heap(void);
 void rb_objspace_set_event_hook(const rb_event_flag_t event);
 VALUE rb_objspace_gc_enable(struct rb_objspace *);
 VALUE rb_objspace_gc_disable(struct rb_objspace *);
diff --git a/process.c b/process.c
index 9605036c64..daf3456bfd 100644
--- a/process.c
+++ b/process.c
@@ -115,7 +115,6 @@ int initgroups(const char *, rb_gid_t);
 #include "ruby/thread.h"
 #include "ruby/util.h"
 #include "vm_core.h"
-#include "vm_sync.h"
 #include "ruby/ractor.h"
 
 /* define system APIs */
@@ -8511,37 +8510,6 @@ static VALUE rb_mProcUID;
 static VALUE rb_mProcGID;
 static VALUE rb_mProcID_Syscall;
 
-/*
- *  call-seq:
- *     Process.warmup    -> true
- *
- *  Notify the Ruby virtual machine that the boot sequence is finished,
- *  and that now is a good time to optimize the application. This is useful
- *  for long running applications.
- *
- *  This method is expected to be called at the end of the application boot.
- *  If the application is deployed using a pre-forking model, +Process.warmup+
- *  should be called in the original process before the first fork.
- *
- *  The actual optimizations performed are entirely implementation specific
- *  and may change in the future without notice.
- *
- *  On CRuby, +Process.warmup+:
- *
- *  * Perform a major GC.
- *  * Compacts the heap.
- *  * Promotes all surviving objects to the old generation.
- */
-
-static VALUE
-proc_warmup(VALUE _)
-{
-    RB_VM_LOCK_ENTER();
-    rb_gc_prepare_heap();
-    RB_VM_LOCK_LEAVE();
-    return Qtrue;
-}
-
 
 /*
  * Document-module: Process
@@ -8659,8 +8627,6 @@ InitVM_process(void)
     rb_define_module_function(rb_mProcess, "getpriority", proc_getpriority, 2);
     rb_define_module_function(rb_mProcess, "setpriority", proc_setpriority, 3);
 
-    rb_define_module_function(rb_mProcess, "warmup", proc_warmup, 0);
-
 #ifdef HAVE_GETPRIORITY
     /* see Process.setpriority */
     rb_define_const(rb_mProcess, "PRIO_PROCESS", INT2FIX(PRIO_PROCESS));
diff --git a/spec/ruby/core/process/warmup_spec.rb b/spec/ruby/core/process/warmup_spec.rb
deleted file mode 100644
index fbdfd34848..0000000000
--- a/spec/ruby/core/process/warmup_spec.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-require_relative '../../spec_helper'
-
-describe "Process.warmup" do
-  ruby_version_is "3.3" do
-    # The behavior is entirely implementation dependant.
-    # Other implementations are free to just make it a noop
-    it "is implemented" do
-      Process.warmup.should == true
-    end
-  end
-end
diff --git a/test/ruby/test_process.rb b/test/ruby/test_process.rb
index fa25d10353..6e8050a54a 100644
--- a/test/ruby/test_process.rb
+++ b/test/ruby/test_process.rb
@@ -4,7 +4,6 @@ require 'test/unit'
 require 'tempfile'
 require 'timeout'
 require 'rbconfig'
-require 'objspace'
 
 class TestProcess < Test::Unit::TestCase
   RUBY = EnvUtil.rubybin
@@ -2680,11 +2679,4 @@ EOS
       end
     end;
   end if Process.respond_to?(:_fork)
-
-  def test_warmup_promote_all_objects_to_oldgen
-    obj = Object.new
-    refute_includes(ObjectSpace.dump(obj), '"old":true')
-    Process.warmup
-    assert_includes(ObjectSpace.dump(obj), '"old":true')
-  end
 end