The British Rail Class 206 or 3R was a type of Diesel-electric multiple unit (DEMU), introduced in 1964.

By 1964, the majority of services on the Southern Region of British Railways had been converted to diesel and electric operation.

A three-bay luggage area was created in the former EMU carriages to cope with the high level of mail traffic on the Reading to Tonbridge route, while the engines in the former DEMU vehicles were uprated by 100hp.

[1] Following a derailment at Appledore (Kent) in March 1980, 1205 and 1206 were temporarily separated to provide cover for damaged Class 201 vehicles.

Class 205 unit 1113 was involved in a collision at Battersea Park in May 1985, causing two of its three carriages to be damaged and later scrapped.