水轮机是水电站中将水流的动能转化为机械能的设备。 通过水电站的拦河坝将水流集中，让水通过压力水管引至水轮机，冲击水轮机转动，并由水轮机带动与其连接的发电机产生电能。

按工作原理分反击式水轮机冲击式水轮机。

反击式水轮机是利用水流的压力和动能来做功。按水流通过转轮叶片方向不同分为混流式、轴流式、斜流式、贯流式。

冲击式水轮机是利用高速水流冲击叶片或水斗来做功。按冲击方式不同有切击式、斜击式、双击式。

另有一种水泵水轮机是一种可逆式水轮机，即可作水轮机，也可做水泵，分为混流式、轴流式、斜流式三种，一般用于抽水蓄能电站。

A water turbine is a rotary machine that converts kinetic and potential energy of water into mechanical work.

Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now they are mostly used for electric power generation. Water turbines are mostly found in dams to generate electric power from water kinetic energy.