The GNR Small Boiler Class C1 is a class of steam locomotive, the first 4-4-2 or Atlantic type in Great Britain. They were designed by Henry Ivatt in 1897. In total 22 were built between 1898 and 1903 at Doncaster Works. They could reach speeds of up to 90 mph. They were also known as Klondykes.

After the 1923 grouping this class became LNER Class C2, whereas the large boiler engines were LNER Class C1. GNR's own Class C2 Atlantic tank locomotives became LNER Class C12.

22 were produced, but only one has survived into preservation and it was the very first. No. 990 Henry Oakley is preserved as part of the National Collection.