diff --git a/include/cryb/hash.h b/include/cryb/hash.h
index 10c42c2..2de6e88 100644
--- a/include/cryb/hash.h
+++ b/include/cryb/hash.h
@@ -34,7 +34,10 @@
 #define pearson_hash_str	cryb_pearson_hash_str
 #define murmur3_32_hash		cryb_murmur3_32_hash
 
-uint8_t pearson_hash(const void *, size_t len);
+uint16_t fletcher16_hash(const void *, size_t);
+uint32_t fletcher32_hash(const void *, size_t);
+uint64_t fletcher64_hash(const void *, size_t);
+uint8_t pearson_hash(const void *, size_t);
 uint8_t pearson_hash_str(const char *);
 uint32_t murmur3_32_hash(const void *, size_t, uint32_t);
 
diff --git a/lib/hash/Makefile.am b/lib/hash/Makefile.am
index 4c229ae..77d77a3 100644
--- a/lib/hash/Makefile.am
+++ b/lib/hash/Makefile.am
@@ -3,5 +3,8 @@ AM_CPPFLAGS = -I$(top_srcdir)/include
 lib_LTLIBRARIES = libcryb-hash.la
 
 libcryb_hash_la_SOURCES = \
+	fletcher16.c \
+	fletcher32.c \
+	fletcher64.c \
 	murmur3_32.c \
 	pearson.c
diff --git a/lib/hash/fletcher16.c b/lib/hash/fletcher16.c
new file mode 100644
index 0000000..0537aad
--- /dev/null
+++ b/lib/hash/fletcher16.c
@@ -0,0 +1,53 @@
+/*-
+ * Copyright (c) 2015 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "cryb/impl.h"
+
+#include <stdint.h>
+#include <string.h>
+
+#include <cryb/bitwise.h>
+#include <cryb/endian.h>
+#include <cryb/hash.h>
+
+/*
+ * Simple implementation of Fletcher's checksum (16-bit version).
+ */
+uint16_t
+fletcher16_hash(const void *data, size_t len)
+{
+	const uint8_t *bytes;
+	uint16_t c0, c1;
+
+	for (bytes = data, c0 = c1 = 0; len > 0; len--, bytes++) {
+		c0 = (c0 + *bytes) % 0xffU;
+		c1 = (c1 + c0) % 0xffU;
+	}
+	return (c1 << 8 | c0);
+}
diff --git a/lib/hash/fletcher32.c b/lib/hash/fletcher32.c
new file mode 100644
index 0000000..b5b35ed
--- /dev/null
+++ b/lib/hash/fletcher32.c
@@ -0,0 +1,62 @@
+/*-
+ * Copyright (c) 2015 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "cryb/impl.h"
+
+#include <stdint.h>
+#include <string.h>
+
+#include <cryb/bitwise.h>
+#include <cryb/endian.h>
+#include <cryb/hash.h>
+
+/*
+ * Simple implementation of Fletcher's checksum (32-bit version).  The
+ * input length is zero-padded to the nearest multiple of 2 bytes.
+ */
+uint32_t
+fletcher32_hash(const void *data, size_t len)
+{
+	const uint8_t *bytes;
+	uint32_t c0, c1;
+	uint16_t w;
+
+	for (bytes = data, c0 = c1 = 0; len > 1; len -= 2, bytes += 2) {
+		/* replace with be16toh() if input is aligned */
+		w = be16dec(bytes);
+		c0 = (c0 + w) % 0xffffU;
+		c1 = (c1 + c0) % 0xffffU;
+	}
+	if (len > 0) {
+		w = bytes[0] << 8;
+		c0 = (c0 + w) % 0xffffffffU;
+		c1 = (c1 + c0) % 0xffffffffU;
+	}
+	return (c1 << 16 | c0);
+}
diff --git a/lib/hash/fletcher64.c b/lib/hash/fletcher64.c
new file mode 100644
index 0000000..42fb251
--- /dev/null
+++ b/lib/hash/fletcher64.c
@@ -0,0 +1,66 @@
+/*-
+ * Copyright (c) 2015 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "cryb/impl.h"
+
+#include <stdint.h>
+#include <string.h>
+
+#include <cryb/bitwise.h>
+#include <cryb/endian.h>
+#include <cryb/hash.h>
+
+/*
+ * Simple implementation of Fletcher's checksum (64-bit version).  The
+ * input length is zero-padded to the nearest multiple of 4 bytes.
+ */
+uint64_t
+fletcher64_hash(const void *data, size_t len)
+{
+	const uint8_t *bytes;
+	uint64_t c0, c1;
+	uint32_t w;
+
+	for (bytes = data, c0 = c1 = 0; len > 3; len -= 4, bytes += 4) {
+		/* replace with be32toh() if input is aligned */
+		w = be32dec(bytes);
+		c0 = (c0 + w) % 0xffffffffU;
+		c1 = (c1 + c0) % 0xffffffffU;
+	}
+	if (len > 0) {
+		w = bytes[0] << 24;
+		if (len > 1)
+			w |= bytes[1] << 16;
+		if (len > 2)
+			w |= bytes[2] << 8;
+		c0 = (c0 + w) % 0xffffffffU;
+		c1 = (c1 + c0) % 0xffffffffU;
+	}
+	return (c1 << 32 | c0);
+}
diff --git a/t/Makefile.am b/t/Makefile.am
index 83f50a8..d87b033 100644
--- a/t/Makefile.am
+++ b/t/Makefile.am
@@ -103,7 +103,8 @@ t_sha512_openssl_LDADD = $(libt) $(OPENSSL_LDADD) $(RT_LIBS)
 endif
 
 # libcryb-hash
-TESTS += t_murmur3_32 t_pearson
+TESTS += t_fletcher t_murmur3_32 t_pearson
+t_fletcher_LDADD = $(libt) $(libhash)
 t_murmur3_32_LDADD = $(libt) $(libhash)
 t_pearson_LDADD = $(libt) $(libhash)
 
diff --git a/t/t_fletcher.c b/t/t_fletcher.c
new file mode 100644
index 0000000..3fb963e
--- /dev/null
+++ b/t/t_fletcher.c
@@ -0,0 +1,162 @@
+/*-
+ * Copyright (c) 2015 Dag-Erling Smørgrav
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "cryb/impl.h"
+
+#include <stdint.h>
+#include <string.h>
+
+#include <cryb/hash.h>
+
+#include "t.h"
+
+struct t_case {
+	const char *desc;
+	const char *data;
+	size_t len;
+	uint16_t sum16;
+	uint32_t sum32;
+	uint64_t sum64;
+};
+
+/***************************************************************************
+ * Test cases
+ */
+static struct t_case t_cases[] = {
+	{
+		.desc	= "len == 0",
+		.data	= "\x01\x02\x03\x04\x05\x06\x07\x08",
+		.len	= 0,
+		.sum16	= 0x00,
+		.sum32	= 0x00,
+		.sum64	= 0x00,
+	},
+	{
+		.desc	= "len == 1",
+		.data	= "\x01\x02\x03\x04\x05\x06\x07\x08",
+		.len	= 1,
+		.sum16	= 0x0101,
+		.sum32	= 0x01000100,
+		.sum64	= 0x0100000001000000,
+	},
+	{
+		.desc	= "len == 2",
+		.data	= "\x01\x02\x03\x04\x05\x06\x07\x08",
+		.len	= 2,
+		.sum16	= 0x0403,
+		.sum32	= 0x01020102,
+		.sum64	= 0x0102000001020000,
+	},
+	{
+		.desc	= "len == 3",
+		.data	= "\x01\x02\x03\x04\x05\x06\x07\x08",
+		.len	= 3,
+		.sum16	= 0x0a06,
+		.sum32	= 0x05040402,
+		.sum64	= 0x102030001020300,
+	},
+	{
+		.desc	= "len == 4",
+		.data	= "\x01\x02\x03\x04\x05\x06\x07\x08",
+		.len	= 4,
+		.sum16	= 0x140a,
+		.sum32	= 0x05080406,
+		.sum64	= 0x0102030401020304,
+	},
+	{
+		.desc	= "len == 5",
+		.data	= "\x01\x02\x03\x04\x05\x06\x07\x08",
+		.len	= 5,
+		.sum16	= 0x230f,
+		.sum32	= 0x0e0e0906,
+		.sum64	= 0x0704060806020304,
+	},
+	{
+		.desc	= "len == 6",
+		.data	= "\x01\x02\x03\x04\x05\x06\x07\x08",
+		.len	= 6,
+		.sum16	= 0x3815,
+		.sum32	= 0x0e14090c,
+		.sum64	= 0x070a060806080304,
+	},
+	{
+		.desc	= "len == 7",
+		.data	= "\x01\x02\x03\x04\x05\x06\x07\x08",
+		.len	= 7,
+		.sum16	= 0x541c,
+		.sum32	= 0x1e20100c,
+		.sum64	= 0x070a0d0806080a04,
+	},
+	{
+		.desc	= "len == 8",
+		.data	= "\x01\x02\x03\x04\x05\x06\x07\x08",
+		.len	= 8,
+		.sum16	= 0x7824,
+		.sum32	= 0x1e281014,
+		.sum64	= 0x070a0d1006080a0c,
+	},
+};
+
+/***************************************************************************
+ * Test function
+ */
+static int
+t_fletcher(char **desc CRYB_UNUSED, void *arg)
+{
+	struct t_case *t = arg;
+	int ret;
+
+	ret = t_compare_x16(t->sum16, fletcher16_hash(t->data, t->len)) &
+	    t_compare_x32(t->sum32, fletcher32_hash(t->data, t->len)) &
+	    t_compare_x64(t->sum64, fletcher64_hash(t->data, t->len));
+	return (ret);
+}
+
+
+/***************************************************************************
+ * Boilerplate
+ */
+
+int
+t_prepare(int argc, char *argv[])
+{
+	int i, n;
+
+	(void)argc;
+	(void)argv;
+	n = sizeof t_cases / sizeof t_cases[0];
+	for (i = 0; i < n; ++i)
+		t_add_test(t_fletcher, &t_cases[i], t_cases[i].desc);
+	return (0);
+}
+
+void
+t_cleanup(void)
+{
+}