The .270 Winchester is a rifle cartridge developed by Winchester Repeating Arms Company in 1923, and it was unveiled in 1925 as a chambering for their bolt-action Model 54 to become arguably the flattest shooting cartridge of its day, only competing with the .300 Holland & Holland Magnum, also introduced in the same year.

The Winchester Repeating Arms Company was a prominent American manufacturer of repeating firearms and ammunition. The firm was established in 1866 by Oliver Winchester and was located in New Haven, Connecticut. The firm went into receivership in 1931 and was bought by the Western Cartridge Company, a forerunner of the Olin Corporation. The Winchester brand name is still owned by the Olin Corporation, which makes ammunition under that name. The Winchester name is also used under license for firearms produced by two subsidiaries of the Herstal Group – FN Herstal of Belgium and the Browning Arms Company of Ogden, Utah.