The A404 is a road in the United Kingdom that starts at Paddington in London and terminates near Maidenhead in Berkshire.

The road initially follows a course through north-west London via Harlesden, Wembley, Harrow, Northwood and Rickmansworth.

It is also the name given to the immediate surrounding area of Queens Park and Kensal Green, straddling the NW10, W10, W2 and W9 postcodes.

[6] The 1950 film The Blue Lamp is set around Harrow Road and features it prominently.

"[7] The A404(M) is a motorway in Berkshire, England and can be referred to as the Maidenhead and Marlow Bypass or M4/M40 link road.

A new spur, the A308(M), was built to maintain access to the A308 and connected with the A404(M) and the M4 at the same grade separated roundabout.