diff --git a/Makefile b/Makefile
index 1cec251f43..81075c38a2 100644
--- a/Makefile
+++ b/Makefile
@@ -2264,6 +2264,10 @@ ifdef USE_ENHANCED_BASIC_REGULAR_EXPRESSIONS
 	COMPAT_CFLAGS += -DUSE_ENHANCED_BASIC_REGULAR_EXPRESSIONS
 	COMPAT_OBJS += compat/regcomp_enhanced.o
 endif
+ifdef DARWIN_REGEXEC
+	COMPAT_OBJS += compat/darwin/regexec.o
+	BASIC_CFLAGS += -DDARWIN_REGEXEC
+endif
 endif
 ifdef NATIVE_CRLF
 	BASIC_CFLAGS += -DNATIVE_CRLF
diff --git a/compat/darwin.h b/compat/darwin.h
new file mode 100644
index 0000000000..6fbdc34560
--- /dev/null
+++ b/compat/darwin.h
@@ -0,0 +1,8 @@
+#ifndef COMPAT_DARWIN_H
+#define COMPAT_DARWIN_H
+
+int darwin_regexec_buf(const regex_t *preg, const char *buf, size_t size,
+		       size_t nmatch, regmatch_t pmatch[], int eflags);
+#define regexec_buf darwin_regexec_buf
+
+#endif
diff --git a/compat/darwin/regexec.c b/compat/darwin/regexec.c
new file mode 100644
index 0000000000..13fb7d5946
--- /dev/null
+++ b/compat/darwin/regexec.c
@@ -0,0 +1,91 @@
+#include "git-compat-util.h"
+
+#include <wchar.h>
+
+/*
+ * Darwin's TRE regex engine leaks an internal buffer when it encounters an
+ * invalid multibyte sequence.  Since the leak has already happened when
+ * regexec() reports REG_ILLSEQ, keep invalid bytes out of regexec() by
+ * searching each valid segment separately.
+ */
+
+/*
+ * Search buf[start, end), where size is the full size of buf.  REG_STARTEND
+ * keeps match offsets relative to buf.  Do not let an internal segment create
+ * a false beginning or end of line.
+ */
+static int regexec_segment(const regex_t *preg, const char *buf,
+			   size_t size, size_t start, size_t end,
+			   size_t nmatch, regmatch_t pmatch[], int eflags)
+{
+	eflags |= REG_STARTEND;
+	if (start > 0)
+		eflags |= REG_NOTBOL;
+	if (end < size)
+		eflags |= REG_NOTEOL;
+	pmatch[0].rm_so = start;
+	pmatch[0].rm_eo = end;
+	return regexec(preg, buf, nmatch, pmatch, eflags);
+}
+
+int darwin_regexec_buf(const regex_t *preg, const char *buf, size_t size,
+		       size_t nmatch, regmatch_t pmatch[], int eflags)
+{
+	size_t seg_start = 0, i = 0;
+	mbstate_t mbs;
+
+	assert(nmatch > 0 && pmatch);
+
+	/*
+	 * A single-byte locale cannot contain an invalid multibyte sequence,
+	 * so use regexec() directly.
+	 */
+	if (MB_CUR_MAX == 1) {
+		pmatch[0].rm_so = 0;
+		pmatch[0].rm_eo = size;
+		return regexec(preg, buf, nmatch, pmatch, eflags | REG_STARTEND);
+	}
+
+	memset(&mbs, 0, sizeof(mbs));
+	while (i < size) {
+		unsigned char c = (unsigned char)buf[i];
+		size_t n;
+
+		if (c < 0x80) {
+			i++;
+			continue;
+		}
+
+		n = mbrtowc(NULL, buf + i, size - i, &mbs);
+		if (!n)
+			n = 1;
+		if (n != (size_t)-1 && n != (size_t)-2) {
+			i += n;
+			continue;
+		}
+
+		/*
+		 * -1 denotes an encoding error; -2 denotes an incomplete
+		 * trailing sequence.  In either case, buf[i] cannot begin a
+		 * complete valid character within this buffer.  Search an
+		 * empty initial segment to preserve zero-width matches at the
+		 * true beginning.
+		 */
+		if (i > seg_start || i == 0) {
+			int ret = regexec_segment(preg, buf, size, seg_start, i,
+						  nmatch, pmatch, eflags);
+			if (ret != REG_NOMATCH)
+				return ret;
+		}
+		i++;
+		seg_start = i;
+		memset(&mbs, 0, sizeof(mbs));
+	}
+
+	/*
+	 * Search the final segment even when it is empty, so an empty buffer
+	 * or a buffer ending in invalid bytes still has its true end.
+	 */
+	return regexec_segment(preg, buf, size, seg_start, size,
+			       nmatch, pmatch, eflags);
+}
diff --git a/config.mak.uname b/config.mak.uname
index 9ebd240378..4660ff3e8a 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -154,6 +154,7 @@ ifeq ($(uname_S),Darwin)
 	HAVE_DEV_TTY = YesPlease
 	COMPAT_OBJS += compat/precompose_utf8.o
 	BASIC_CFLAGS += -DPRECOMPOSE_UNICODE
+	DARWIN_REGEXEC = YesPlease
 	BASIC_CFLAGS += -DPROTECT_HFS_DEFAULT=1
 	HAVE_BSD_SYSCTL = YesPlease
 	FREAD_READS_DIRECTORIES = UnfortunatelyYes
diff --git a/contrib/buildsystems/CMakeLists.txt b/contrib/buildsystems/CMakeLists.txt
index a57c4b464f..83e8b710ec 100644
--- a/contrib/buildsystems/CMakeLists.txt
+++ b/contrib/buildsystems/CMakeLists.txt
@@ -519,6 +519,9 @@ if(NOT HAVE_REGEX)
 	include_directories(${CMAKE_SOURCE_DIR}/compat/regex)
 	list(APPEND compat_SOURCES compat/regex/regex.c )
 	add_compile_definitions(NO_REGEX NO_MBSUPPORT GAWK)
+elseif(APPLE)
+	list(APPEND compat_SOURCES compat/darwin/regexec.c)
+	add_compile_definitions(DARWIN_REGEXEC)
 endif()
 
 
diff --git a/git-compat-util.h b/git-compat-util.h
index 8809776407..96995c65d3 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -162,6 +162,9 @@ static inline int is_xplatform_dir_sep(int c)
 #include "compat/win32/path-utils.h"
 #include "compat/msvc.h"
 #endif
+#ifdef DARWIN_REGEXEC
+#include "compat/darwin.h"
+#endif
 
 /* used on Mac OS X */
 #ifdef PRECOMPOSE_UNICODE
@@ -992,6 +995,7 @@ static inline int strtol_i(char const *s, int base, int *result)
 #error "Git requires REG_STARTEND support. Compile with NO_REGEX=NeedsStartEnd"
 #endif
 
+#ifndef regexec_buf
 static inline int regexec_buf(const regex_t *preg, const char *buf, size_t size,
 			      size_t nmatch, regmatch_t pmatch[], int eflags)
 {
@@ -1000,6 +1004,7 @@ static inline int regexec_buf(const regex_t *preg, const char *buf, size_t size,
 	pmatch[0].rm_eo = size;
 	return regexec(preg, buf, nmatch, pmatch, eflags | REG_STARTEND);
 }
+#endif
 
 #ifdef USE_ENHANCED_BASIC_REGULAR_EXPRESSIONS
 int git_regcomp(regex_t *preg, const char *pattern, int cflags);
diff --git a/meson.build b/meson.build
index 3247697f74..53c4816323 100644
--- a/meson.build
+++ b/meson.build
@@ -1387,6 +1387,11 @@ if not get_option('b_sanitize').contains('address') and get_option('regex').allo
     libgit_c_args += '-DUSE_ENHANCED_BASIC_REGULAR_EXPRESSIONS'
     compat_sources += 'compat/regcomp_enhanced.c'
   endif
+
+  if host_machine.system() == 'darwin'
+    libgit_c_args += '-DDARWIN_REGEXEC'
+    compat_sources += 'compat/darwin/regexec.c'
+  endif
 elif not get_option('regex').enabled()
   libgit_c_args += [
     '-DNO_REGEX',
diff --git a/t/t7810-grep.sh b/t/t7810-grep.sh
index d61c4a4d73..149654e7f4 100755
--- a/t/t7810-grep.sh
+++ b/t/t7810-grep.sh
@@ -89,6 +89,10 @@ test_expect_success setup '
 	function dummy() {}
 	EOF
 	printf "\200\nASCII\n" >invalid-utf8 &&
+	printf "before\346world\n" >invalid-utf8-embedded &&
+	printf "a\346b\347c\n" >invalid-utf8-multi &&
+	printf "\346world\n" >invalid-utf8-leading &&
+	printf "before\346\n" >invalid-utf8-trailing &&
 	if test_have_prereq FUNNYNAMES
 	then
 		echo unusual >"\"unusual\" pathname" &&
@@ -595,6 +599,39 @@ test_expect_success MB_REGEX 'grep two chars in single-char multibyte file' '
 	LC_ALL=en_US.UTF-8 test_expect_code 1 git grep ".." reverse-question-mark
 '
 
+test_expect_success MACOS,MB_REGEX 'grep matches valid text on both sides of invalid UTF-8' '
+	LC_ALL=en_US.UTF-8 git grep -h "befo[r]e" invalid-utf8-embedded >actual &&
+	test_cmp invalid-utf8-embedded actual &&
+	LC_ALL=en_US.UTF-8 git grep -h "worl[d]" invalid-utf8-embedded >actual &&
+	test_cmp invalid-utf8-embedded actual &&
+	LC_ALL=en_US.UTF-8 git grep -h -o "worl[d]" invalid-utf8-embedded >actual &&
+	echo world >expected &&
+	test_cmp expected actual
+'
+
+test_expect_success MACOS,MB_REGEX 'grep matches a run between two invalid sequences' '
+	LC_ALL=en_US.UTF-8 git grep -h "[b]" invalid-utf8-multi >actual &&
+	test_cmp invalid-utf8-multi actual
+'
+
+test_expect_success MB_REGEX 'grep does not anchor ^ or $ inside an invalid-byte line' '
+	test_expect_code 1 env LC_ALL=en_US.UTF-8 \
+		git grep -h "^world" invalid-utf8-embedded &&
+	test_expect_code 1 env LC_ALL=en_US.UTF-8 \
+		git grep -h "before\$" invalid-utf8-embedded
+'
+
+test_expect_success MACOS,MB_REGEX 'grep anchors ^ and $ at true line ends past invalid UTF-8' '
+	LC_ALL=en_US.UTF-8 git grep -h "^before" invalid-utf8-embedded >actual &&
+	test_cmp invalid-utf8-embedded actual &&
+	LC_ALL=en_US.UTF-8 git grep -h "world\$" invalid-utf8-embedded >actual &&
+	test_cmp invalid-utf8-embedded actual &&
+	LC_ALL=en_US.UTF-8 git grep -h "^" invalid-utf8-leading >actual &&
+	test_cmp invalid-utf8-leading actual &&
+	LC_ALL=en_US.UTF-8 git grep -h "\$" invalid-utf8-trailing >actual &&
+	test_cmp invalid-utf8-trailing actual
+'
+
 cat >expected <<EOF
 file
 EOF