diff --git a/src/lib/Makefile.inc b/src/lib/Makefile.inc
index 0c6473be..5cc61e01 100644
--- a/src/lib/Makefile.inc
+++ b/src/lib/Makefile.inc
@@ -73,7 +73,6 @@ CSOURCES = ares__addrinfo2hostent.c	\
   ares_timeout.c			\
   ares_update_servers.c	\
   ares_version.c			\
-  bitncmp.c				\
   inet_net_pton.c			\
   inet_ntop.c				\
   windows_port.c
@@ -98,7 +97,6 @@ HHEADERS = ares__buf.h			\
   ares_strcasecmp.h			\
   ares_str.h				\
   ares_strsplit.h			\
-  bitncmp.h				\
   ares_setup.h				\
   setup_once.h
 
diff --git a/src/lib/ares_getaddrinfo.c b/src/lib/ares_getaddrinfo.c
index d5c440b2..af5b5a6e 100644
--- a/src/lib/ares_getaddrinfo.c
+++ b/src/lib/ares_getaddrinfo.c
@@ -57,7 +57,6 @@
 #endif
 
 #include "ares.h"
-#include "bitncmp.h"
 #include "ares_private.h"
 #include "ares_dns.h"
 
diff --git a/src/lib/ares_gethostbyname.c b/src/lib/ares_gethostbyname.c
index f0316de4..299c35b4 100644
--- a/src/lib/ares_gethostbyname.c
+++ b/src/lib/ares_gethostbyname.c
@@ -45,7 +45,6 @@
 
 #include "ares.h"
 #include "ares_inet_net_pton.h"
-#include "bitncmp.h"
 #include "ares_platform.h"
 #include "ares_private.h"
 
diff --git a/src/lib/bitncmp.c b/src/lib/bitncmp.c
deleted file mode 100644
index 0296316d..00000000
--- a/src/lib/bitncmp.c
+++ /dev/null
@@ -1,64 +0,0 @@
-/*
- * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
- * Copyright (c) 1996,1999 by Internet Software Consortium.
- *
- * Permission to use, copy, modify, and distribute this software for any
- * purpose with or without fee is hereby granted, provided that the above
- * copyright notice and this permission notice appear in all copies.
- *
- * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
- * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
- * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
- * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
- * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
- * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
- * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
- *
- * SPDX-License-Identifier: MIT
- */
-
-#ifndef HAVE_BITNCMP
-
-#  include "ares_setup.h"
-#  include "bitncmp.h"
-
-/*
- * int
- * bitncmp(l, r, n)
- *	compare bit masks l and r, for n bits.
- * return:
- *	<0, >0, or 0 in the libc tradition.
- * note:
- *	network byte order assumed.  this means 192.5.5.240/28 has
- *	0x11110000 in its fourth octet.
- * author:
- *	Paul Vixie (ISC), June 1996
- */
-int ares__bitncmp(const void *l, const void *r, size_t n)
-{
-  size_t       lb;
-  size_t       rb;
-  ares_ssize_t x;
-  size_t       b;
-
-  b = n / 8;
-  x = memcmp(l, r, b);
-  if (x || (n % 8) == 0) {
-    return (int)x;
-  }
-
-  lb = ((const unsigned char *)l)[b];
-  rb = ((const unsigned char *)r)[b];
-  for (b = n % 8; b > 0; b--) {
-    if ((lb & 0x80) != (rb & 0x80)) {
-      if (lb & 0x80) {
-        return (1);
-      }
-      return (-1);
-    }
-    lb <<= 1;
-    rb <<= 1;
-  }
-  return (0);
-}
-#endif
diff --git a/src/lib/bitncmp.h b/src/lib/bitncmp.h
deleted file mode 100644
index 0c4b9c39..00000000
--- a/src/lib/bitncmp.h
+++ /dev/null
@@ -1,35 +0,0 @@
-/* MIT License
- *
- * Copyright (c) 2005 Dominick Meglio
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice (including the next
- * paragraph) shall be included in all copies or substantial portions of the
- * Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
- *
- * SPDX-License-Identifier: MIT
- */
-#ifndef __ARES_BITNCMP_H
-#define __ARES_BITNCMP_H
-
-#ifndef HAVE_BITNCMP
-int ares__bitncmp(const void *l, const void *r, size_t n);
-#else
-#  define ares__bitncmp(x, y, z) bitncmp(x, y, z)
-#endif
-
-#endif /* __ARES_BITNCMP_H */
diff --git a/test/ares-test-internal.cc b/test/ares-test-internal.cc
index 4a39077f..5ba15bbd 100644
--- a/test/ares-test-internal.cc
+++ b/test/ares-test-internal.cc
@@ -38,7 +38,6 @@ extern "C" {
 #include "ares_strsplit.h"
 #include "ares_private.h"
 #include "ares__htable.h"
-#include "bitncmp.h"
 
 #ifdef HAVE_ARPA_INET_H
 #include <arpa/inet.h>
@@ -275,30 +274,6 @@ TEST_F(LibraryTest, MallocDataFail) {
   EXPECT_EQ(nullptr, ares_malloc_data(ARES_DATATYPE_MX_REPLY));
 }
 
-TEST(Misc, Bitncmp) {
-  byte a[4] = {0x80, 0x01, 0x02, 0x03};
-  byte b[4] = {0x80, 0x01, 0x02, 0x04};
-  byte c[4] = {0x01, 0xFF, 0x80, 0x02};
-  EXPECT_GT(0, ares__bitncmp(a, b, sizeof(a)*8));
-  EXPECT_LT(0, ares__bitncmp(b, a, sizeof(a)*8));
-  EXPECT_EQ(0, ares__bitncmp(a, a, sizeof(a)*8));
-
-  for (size_t ii = 1; ii < (3*8+5); ii++) {
-    EXPECT_EQ(0, ares__bitncmp(a, b, ii));
-    EXPECT_EQ(0, ares__bitncmp(b, a, ii));
-    EXPECT_LT(0, ares__bitncmp(a, c, ii));
-    EXPECT_GT(0, ares__bitncmp(c, a, ii));
-  }
-
-  // Last byte differs at 5th bit
-  EXPECT_EQ(0, ares__bitncmp(a, b, 3*8 + 3));
-  EXPECT_EQ(0, ares__bitncmp(a, b, 3*8 + 4));
-  EXPECT_EQ(0, ares__bitncmp(a, b, 3*8 + 5));
-  EXPECT_GT(0, ares__bitncmp(a, b, 3*8 + 6));
-  EXPECT_GT(0, ares__bitncmp(a, b, 3*8 + 7));
-}
-
-
 TEST_F(LibraryTest, ReadLine) {
   TempFile temp("abcde\n0123456789\nXYZ\n012345678901234567890\n\n");
   FILE *fp = fopen(temp.filename(), "r");