The Great Northern Railway M-1 was a class of American 2-6-8-0 locomotives introduced in 1910. A total of 35 of these Mallet locomotives were built by Baldwin Locomotive Works for Great Northern Railway (GN) in two batches; the first 10 in December 1909 and a further 25 in June to August 1910. These engines were unusual because of their uneven driving wheel sets, the front having six driving wheels while the rear had eight.
All M-1's were converted from compound to simple-expansion cylinders from 1926 to 1927 and reclassified M-2. 22 M-2's were dismantled between 1929 and 1931, with parts being recycled for the new class O-7 Mikados numbered 3376-3396 in 1930. Three O7 Mikados were rebuilt to O8 Mikados numbered 3397-3399 in 1932. The 13 unrebuilt M-2's lasted until dieselisation and were sold for scrap between 1949 and 1954. No examples were preserved in any form.