diff --git a/plugins/message-timestamp/Makefile b/plugins/message-timestamp/Makefile
new file mode 100644
index 00000000..77563d71
--- /dev/null
+++ b/plugins/message-timestamp/Makefile
@@ -0,0 +1,4 @@
+all : mosquitto_timestamp.so
+
+mosquitto_timestamp.so : mosquitto_timestamp.c
+	$(CC) -I../../include -fPIC -shared $< -o $@
diff --git a/plugins/message-timestamp/mosquitto_timestamp.c b/plugins/message-timestamp/mosquitto_timestamp.c
new file mode 100644
index 00000000..b689c2f1
--- /dev/null
+++ b/plugins/message-timestamp/mosquitto_timestamp.c
@@ -0,0 +1,69 @@
+/*
+Copyright (c) 2020 Roger Light <roger@atchoo.org>
+
+All rights reserved. This program and the accompanying materials
+are made available under the terms of the Eclipse Public License v1.0
+and Eclipse Distribution License v1.0 which accompany this distribution.
+ 
+The Eclipse Public License is available at
+   http://www.eclipse.org/legal/epl-v10.html
+and the Eclipse Distribution License is available at
+  http://www.eclipse.org/org/documents/edl-v10.php.
+ 
+Contributors:
+   Roger Light - initial implementation and documentation.
+*/
+
+/*
+ * Add an MQTT v5 user-property with key "timestamp" and value of timestamp in ISO-8601 format to all messages.
+ *
+ * Compile with:
+ *   gcc -I<path to mosquitto-repo/include> -fPIC -shared mosquitto_timestamp.c -o mosquitto_timestamp.so
+ *
+ * Use in config with:
+ *
+ *   plugin /path/to/mosquitto_timestamp.so
+ *
+ * Note that this only works on Mosquitto 2.0 or later.
+ */
+
+
+#include <stdio.h>
+#include <time.h>
+
+#include "mosquitto_broker.h"
+#include "mosquitto_plugin.h"
+#include "mosquitto.h"
+#include "mqtt_protocol.h"
+
+static mosquitto_plugin_id_t *mosq_pid = NULL;
+
+static int callback_message(int event, void *event_data, void *userdata)
+{
+	struct mosquitto_evt_message *ed = event_data;
+	struct timespec ts;
+	struct tm *ti;
+	char time_buf[25];
+
+	clock_gettime(CLOCK_REALTIME, &ts);
+	ti = gmtime(&ts.tv_sec);
+	strftime(time_buf, sizeof(time_buf), "%Y-%m-%dT%H:%M:%SZ", ti);
+
+	return mosquitto_property_add_string_pair(&ed->properties, MQTT_PROP_USER_PROPERTY, "timestamp", time_buf);
+}
+
+int mosquitto_plugin_version(void)
+{
+	return 5;
+}
+
+int mosquitto_plugin_init(mosquitto_plugin_id_t *identifier, void **user_data, struct mosquitto_opt *opts, int opt_count)
+{
+	mosq_pid = identifier;
+	return mosquitto_callback_register(mosq_pid, MOSQ_EVT_MESSAGE, callback_message, NULL, NULL);
+}
+
+int mosquitto_plugin_cleanup(void *user_data, struct mosquitto_opt *opts, int opt_count)
+{
+	return mosquitto_callback_unregister(mosq_pid, MOSQ_EVT_MESSAGE, callback_message, NULL);
+}