Comet Crommelin, also known as Comet Pons-Coggia-Winnecke-Forbes, is a periodic comet in the solar system named after the British astronomer Andrew C. D. Crommelin who calculated its orbit in 1930. It is one of only four comets not named after their discoverer(s), the other three being Comets Halley, Encke, and Lexell.

The first observation was by Jean-Louis Pons (Marseille, France) on February 23, 1818, he followed the comet up until February 27 but was prevented further by bad weather. Johann Franz Encke attempted to calculate the orbit but was left with very large errors.

In 1872, John R. Hind produced a rough orbital calculation and observed it was close to that of Comet Biela, based on these observations, Edmund Weiss later speculated it may have been part of Biela's comet.

The next observation was on November 10, 1873 by Jérôme E. Coggia (Marseille, France), and again on November 11 by Friedrich A. T. Winnecke (Strasbourg, France), but it was lost by November 16. Weiss and Hind took up the calculations and tried to match it again with the 1818 appearance.

A third discovery was by Alexander F. I. Forbes (Cape Town, South Africa) on November 19, 1928, and confirmed by Harry E. Wood (Union Observatory, South Africa) on November 21. It was Crommelin who eventually established the orbit and finally linked the 1818 (Pons) and 1873 (Coggia-Winnecke) comets to it. (see Lost comet)

During the 2011 perihelion passage 27P/Crommelin was recovered on 12 May 2011 at apparent magnitude 18.7.