The Great Northern Railway (GNR) Class C1 is a type of 4-4-2 steam locomotive. Much like their small boiler cousins, they were capable of reaching speeds of up to 90 mph. They were also known as Large Atlantics.

The C1 Class, as it was known under both GNR & LNER classifications, was designed by Henry Ivatt as an enlarged version of what became the LNER C2 Class. The principle of the design was to produce a powerful, free-steaming engine to haul the fastest and heaviest express trains on the Great Northern. They could thus be seen as the start of the East Coast 'Big Engine' policy. None were ever named.

94 were built, one, ex GNR 251, later LNER 2800, survives in preservation.