The Allison Model 250, now known as the Rolls-Royce M250, is a highly successful turboshaft engine family, originally developed by the Allison Engine Company in the early 1960s. The Model 250 has been produced by Rolls-Royce since it acquired Allison in 1995.

The Allison Engine Company was an American aircraft engine manufacturer. Shortly after the death of James Allison in 1929 the company was purchased by the Fisher brothers. Fisher sold the company to General Motors, which owned it for most of its history. It was acquired by Rolls-Royce plc in 1995 to become the US subsidiary, Rolls-Royce North America.