The M49 motorway is a small motorway west of Bristol, England, that forms a shortcut between the M5 and the Second Severn Crossing on the M4 motorway. It begins at junction 18a of the M5, and merges with the M4 at junction 22, just before the Second Severn Crossing, cutting journey times for traffic to and from Avonmouth docks, Central and southern Bristol and South West England. It also fulfils the dual role of providing a bypass for the busy stretch of the M5 between the Avonmouth Bridge and the M4 in case of accidents, etc.

The motorway was constructed in the mid-1990s at the same time as the bridge. It is unique on the British network for being the only motorway accessible only from other motorways. The original plans provided for an intermediate junction with the A403 to serve an expanded industrial area, but neither this or the junction came to fruition.