Johannes Hevelius or Johann Hewelke or Johannes Hewel (German) or Jan Heweliusz (Polish) (January 28, 1611-January 28, 1687) was an astronomer; called the founder of lunar topography.

He was born in Gdansk, Polish-Lithuanian Commonwealth in 1611 to family of wealthy brewing merchants of Czech origins. He studied jurisprudence at Leiden in 1630; travelled in England and France; and in 1634 settled in his native town as a brewer and town councillor. From 1639 his chief interest became centered in astronomy, though he took, throughout his life, a leading part in municipal affairs. In 1641 he built an observatory in his house, provided with a splendid instrumental outfit, including ultimately a tubeless telescope of 150 ft. focal length, constructed by himself. It was visited, on January 29, 1660 by King John II of Poland and Queen Maria Gonzaga .

Hevelius made observations of sunspots, 1642-1645, devoted four years to charting the lunar surface, discovered the Moon's libration in longitude, and published his results in Selenographia (1647), a work which entitles him to be called the founder of lunar topography . He discovered four comets in the several years (1652, 1661, 1672 and 1677) and suggested the revolution of such bodies in parabolic tracks round the sun.

On the September 26, 1679 his observatory, instruments and books were maliciously destroyed by fire, the catastrophe being described in the preface to his Annus climactericus (1685). He promptly repaired the damage, so far as to enable him to observe the great comet of December 1680; but his health suffered from the shock, and he died on the January 28, 1687.

Among his works were:

• Historiola Mirae (1662), in which he named the periodic variable star Omicron Ceti "Mira", or "the Wonderful".
• Prodromus cometicus (1665)
• Cometographia (1668)
• Machina coelestis (first part, 1673), containing a description of his instruments; the second part (1679) is extremely rare, nearly the whole issue having perished in the conflagration of 1679.
• The observations made by Hevelius on the variable star named by him, Mira, are included in Annus climactericus.
• His catalogue of 1564 stars appeared posthumously in Prodromus astronomiae (1690). Its value was much impaired by his preference of the antique pinnules to telescopic sights on quadrants. This led to an acrimonious controversy with Robert Hooke.
• In an atlas of 56 sheets, corresponding to his catalogue, and entitled Firmamentum Sobiescianum (1690), he delineated seven new constellations, still in use.

Hevelius had his book printed in his own house, at lavish expense, and himself not only designed but engraved many of the plates.