John Calley (also spelt Cawley) (1663 – May 1725, The Hague),^[1] was a metalworker, plumber and glass-blower,^[2] who became famous for being Thomas Newcomen's partner. Like Newcomen, he was a member of a Dartmouth family.

He helped develop the Newcomen atmospheric engine. He worked with Newcomen in introducing the engine to the Midlands, operating under the patent of Thomas Savery.^[3] The engine they created was a variation on the then current technology using a combination of steam cylinders, pistons, surface condensation and the separation of parts that were usually placed together to create this new technology.^[4]

He installed an early Newcomen engine at More Hall Colliery in the grounds of Austhorpe Hall in Leeds, where he is said to have become ill and died during maintenance work.^[5] However, there is also evidence that he died in The Hague in 1725, while trying to secure a foreign patent for another device.^{[citation needed]}