The EMD F3 was a 1,500-horsepower (1,100 kW), B-B freight-hauling diesel locomotive produced between July 1945 and February 1949 by General Motors’ Electro-Motive Division. Final assembly was at GM-EMD's La Grange, Illinois plant. A total of 1,111 cab-equipped lead A units and 696 cabless booster B units were built.
The F3 was the third model in GM-EMD's highly successful F-unit series of cab unit freight diesels, and it was the second most produced of the series. The F3 essentially differed from the EMD F2 in that it used the “new” D12 generator to produce more power, and from the later EMD F7 in electrical equipment. Some late-model F3s had the same D27 traction motors used in the F7, and were nicknamed F5 models.
As built, the only way to distinguish between the F2 and F3 was the nose number panels on the A units, which were small on the F2 and large on the F3 and subsequent locomotives. However, these could and were often altered by the railroad. Few F2s were built, however.
Early versions of the F3 had the "chicken wire" grilles along the top edge of the carbody. Later production featured a distinctive stamped stainless steel grille.
All F-units introduced after the FT have twin exhaust stacks and four radiator fans arranged close together atop their roofs, unlike the FT's four stacks and separated pairs of fans.