When was the steam engine invented?

The first commercially successful steam engine was built by Thomas Newcomen in 1712 to pump water out of mines. It was inefficient, but in the 1760s and 1770s James Watt introduced key improvements, including a separate condenser, that made steam power far more efficient and versatile. Watt engines went on to drive factories, mills, ships, and railways, becoming the beating heart of the Industrial Revolution. The unit of power, the watt, is named in his honour.