The Denham Roundabout is a road junction in Denham, Buckinghamshire. It was originally opened in 1943 in conjunction with the completion of the new Western Avenue route into west London. The Western Avenue took over the classification of the A40, with the previous route to London, via Uxbridge and Ealing, being reclassified as the A4020. The roundabout also included a new link to A412 that formed part of the outer London orbital route.