The British Rail Class 20, otherwise known as an English Electric Type 1, is a class of diesel-electric locomotive. In total, 228 locomotives in the class were built by English Electric between 1957 and 1968, the large number being in part because of the failure of other early designs in the same power range to provide reliable locomotives.

The locomotives were originally numbered D8000–D8199 and D8300–D8327. They are known by railway enthusiasts as "Choppers"

Unusually for British designs, the locomotive had a single cab. This caused serious problems with visibility when travelling nose first, though in these circumstances the driver's view is comparable to that on the steam locomotives that the Class 20s replaced. It was common, however, to find Class 20s paired together at the nose, with their cabs at opposite ends, ensuring that the driver could quite clearly see the road ahead, and a guard can watch the train from the other locomotive without the need for a brakevan.

Now mostly in private use or preservation