The Oxford–Cambridge Arc (formerly the Cambridge – Milton Keynes – Oxford corridor) is a notional arc of agricultural and urban land at about 80 kilometres (50 miles) radius of London, in south central England. It runs between the British university cities of Oxford and Cambridge via Milton Keynes and other settlements in Bedfordshire, Buckinghamshire, Cambridgeshire, Northamptonshire, Oxfordshire at the northern rim of the London commuter belt. It is significant only in economic geography, with little physical geography in common.

The original Oxford to Cambridge (O2C) Arc initiative was launched in 2003 by three English regional development agencies (RDAs), EEDA, EMDA and SEEDA. The aim of the initiative is to promote and accelerate the development of the unique set of educational, research and business assets and activities that characterise the area and in doing so, create an "arc of innovation and entrepreneurial activity that would, in time, be 'best in the field'".

In November 2017, a report for the National Infrastructure Commission (NIC) noted that, "in 2014, the Gross Value Added (GVA) of the "corridor" was £90.5bn (2011 prices); by doubling housebuilding rates in the area, and delivering East West Rail and the Oxford–Cambridge Expressway, this [would] increase by £163bn to a GVA of £250bn". In February 2021, the Government announced plans to develop the concept further, but cancelled the Abingdon–Milton Keynes link of the expressway in March 2021. As of July 2022, East West Rail development continues but the (then) Minister has suggested that the Bedford–Cambridge leg could be cancelled.