diff --git a/configure.ac b/configure.ac
index d251da9915..5e2a67db1b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1825,6 +1825,7 @@ AC_CHECK_FUNCS(lstat)
 AC_CHECK_FUNCS(lutimes)
 AC_CHECK_FUNCS(malloc_usable_size)
 AC_CHECK_FUNCS(malloc_size)
+AC_CHECK_FUNCS(malloc_trim)
 AC_CHECK_FUNCS(mblen)
 AC_CHECK_FUNCS(memalign)
 AC_CHECK_FUNCS(memset_s)
diff --git a/gc.c b/gc.c
index 1331ef21dc..12caa162e7 100644
--- a/gc.c
+++ b/gc.c
@@ -6660,7 +6660,15 @@ gc_start(rb_objspace_t *objspace, int reason)
 
     gc_prof_timer_start(objspace);
     {
-	gc_marks(objspace, do_full_mark);
+        gc_marks(objspace, do_full_mark);
+#ifdef HAVE_MALLOC_TRIM
+        /* [Experimental] Explicitly free all eligible pages to the kernel.  See:
+         *
+         * - https://www.joyfulbikeshedding.com/blog/2019-03-14-what-causes-ruby-memory-bloat.html
+         * - https://bugs.ruby-lang.org/issues/15667
+         */
+        if (do_full_mark) malloc_trim(0);
+#endif
     }
     gc_prof_timer_stop(objspace);