蒸汽涡轮发动机（Steam turbine）是一种截取（将水加热后形成的）蒸汽之动能转换为涡轮转动之动能的机械。相较于原由詹姆斯·瓦特发明的单级往复式蒸汽机，涡轮蒸汽机大幅提高了热效率，更接近热力学中理想的可逆过程，并能提供更大的功率，至今它几乎取代了往复式蒸汽机。使用涡轮蒸汽机发电的电厂叫做热电厂，其特别适用于火力发电和核能发电，世界上大约80%的电能是涡轮蒸汽机所产生。船舶领域主要用于大型舰船。

一具现代蒸汽涡轮发动机总成

1910年制250kw小型蒸汽涡轮发动机

A steam turbine is a device that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Sir Charles Parsons in 1884.

Because the turbine generates rotary motion, it is particularly suited to be used to drive an electrical generator – about 90% of all electricity generation in the United States (1996) is by use of steam turbines. The steam turbine is a form of heat engine that derives much of its improvement in thermodynamic efficiency from the use of multiple stages in the expansion of the steam, which results in a closer approach to the ideal reversible expansion process.