Comet 25D/Neujmin, otherwise known as Comet Neujmin 2, is a periodic comet in the solar system discovered by Grigory N. Neujmin (Simeis) on February 24, 1916.
It was confirmed by George van Biesbroeck (Yerkes Observatory, Wisconsin, United States) and Frank Watson Dyson (Greenwich Observatory, England) on March 1.
A prediction by Andrew Crommelin (Royal Observatory, Greenwich, England) for 1921 was considered unfavourable and no observations were made. The next prediction for 2 January 1927 took into account an unnamed object observed in 1920, but despite searches, nothing was seen.
Consequently, this comet has remained a lost comet since 1927.