The A423 road is a primary A road in England which leads from central Banbury to the A45 near Coventry. It starts in Banbury town centre as Southam Road and goes through the Southam Road Industrial Estate, then just north of Banbury it crosses over the M40, from there it passes close to several Warwickshire villages until it becomes part of the Southam by-pass, it then goes through Long Itchington and Marton before merging with the A45 near Ryton.

Its original route when first classified in 1922 was from Tamworth in Staffordshire to Oxford. In the 1930s the route was extended from Oxford to the A4 near Maidenhead in Berkshire, over parts of the former routes of the A42 and A415. From 1971 to 1990 it joined the then A423(M) motorway at Maidenhead Thicket. A curious feature of the route was a 3-mile (4.8 km) gap between Benson, Oxfordshire and a point 1.2 miles (1.9 km) north west of Nuffield, which resulted from the construction of RAF Benson across the line of the road. The detour though Crowmarsh Gifford was designated the B479 and A4130 rather than A423.