diff --git a/msg/CMakeLists.txt b/msg/CMakeLists.txt
index a0eb898586..b23e8d64a8 100644
--- a/msg/CMakeLists.txt
+++ b/msg/CMakeLists.txt
@@ -101,6 +101,8 @@ set(msg_file_names
 	transponder_report.msg
 	uavcan_parameter_request.msg
 	uavcan_parameter_value.msg
+	ulog_stream.msg
+	ulog_stream_ack.msg
 	vehicle_attitude.msg
 	vehicle_attitude_setpoint.msg
 	vehicle_command_ack.msg
diff --git a/msg/ulog_stream.msg b/msg/ulog_stream.msg
new file mode 100644
index 0000000000..0fe647a6ce
--- /dev/null
+++ b/msg/ulog_stream.msg
@@ -0,0 +1,16 @@
+# Message to stream ULog data from the logger. Corresponds to the LOGGING_DATA
+# mavlink message
+
+# flags bitmasks
+uint8 FLAGS_NEED_ACK = 1     # if set, this message requires to be acked.
+                             # Acked messages are published synchronous: a
+                             # publisher waits for an ack before sending the
+                             # next message
+
+uint8 length                 # length of data
+uint8 first_message_offset   # offset into data where first message starts. This
+                             # can be used for recovery, when a previous message got lost
+uint16 sequence              # allows determine drops
+uint8 flags                  # see FLAGS_*
+uint8[251] data              # ulog data
+
diff --git a/msg/ulog_stream_ack.msg b/msg/ulog_stream_ack.msg
new file mode 100644
index 0000000000..c155b2a875
--- /dev/null
+++ b/msg/ulog_stream_ack.msg
@@ -0,0 +1,7 @@
+# Ack a previously sent ulog_stream message that had
+# the NEED_ACK flag set
+
+int32 ACK_TIMEOUT = 300         # timeout waiting for an ack until we retry to send the message [ms]
+int32 ACK_MAX_TRIES = 9         # maximum amount of tries to (re-)send a message, each time waiting ACK_TIMEOUT ms
+
+uint16 sequence