Philipp Matthäus Hahn (25 November 1739 in Scharnhausen (today part of Ostfildern), Duchy of Württemberg – 2 May 1790 in Echterdingen (today part of Leinfelden-Echterdingen)) was a German pastor, astronomer and inventor.

In about 1763 he devised a precision sundial, or heliochronometer that incorporated the correction for the equation of time.

In 1774 he designed one of the earliest mechanical calculators of which two are known to have survived to the present day. A renowned clockmaker, several horological museums display his works, including the Deutsches Uhrenmuseum which contains a mechanical orrery (planetarium) and a Weltmaschine by the "Priestermechaniker (priest mechanic)".