The A5120 is an A-class road in Bedfordshire, linking the towns of Ampthill and Flitwick to the M1 motorway at Toddington.

[1]: 20  It connects with the M1 at junction 12[2] in close proximity to the Toddington services.

On its route from Ampthill to Toddington, the A5120 serves Westoning and Harlington.

The route previously ran to the old A5 Watling Street at Dunstable (now the A5183), however upon the opening of the A5 Dunstable Northern Bypass, the section between the M1 and the new junction A5 was downgraded to the B5120, about halving the length of the route.

In 2009, the annual average daily traffic flow on the A5120 near Westoning was slightly over 17,000.