汽转球（英语：aeolipile）是已知最早以蒸气发动的机器，在公元一世纪时由亚历山大港的希罗（Hero of Alexandria）发明。

在希罗之前，维特鲁威（Vitruvius）在《建筑十书》（De Architectura）中已提到一种空心并有小开口的黄铜容器，注入水后再用火烧来研究蒸气。当时他已用「æolipylæ」这个字。

汽转球主要是由一个空心的球和一个装有水的密闭锅子以两个空心管子连接在一起，而在锅底加热使水沸腾，锅中的蒸气就通过管子进入球中，最后蒸气会由球体的两旁喷出并使得球体转动。 详细建构图在希罗的《气体力学》（Pneumatics）中有描述。

An aeolipile (or aeolipyle, or eolipile), also known as a Hero's engine, is a simple bladeless radial steam turbine which spins when the central water container is heated. Torque is produced by steam jets exiting the turbine, much like a tip jet or rocket engine. In the 1st century AD, Hero of Alexandria described the device, and many sources give him the credit for its invention.