Kostopil (Ukrainian: Костопіль, IPA: [kosˈtɔpilʲ]; Polish: Kostopol) is a small city on the Zamchysko [uk] river in Rivne Oblast, western Ukraine (historical Volhynia).

Settlement in the town was encouraged by the imperial authorities but it stagnated until a railway station was opened on the Rovno — Vilna line in the late 1890s.

In nearby Janowa Dolina, there were granite and basalt quarries, with railway links to Kostopol station.

The Germans progressively degraded the Jews' position and condition, by enforcing the wearing of yellow stars, imposing forced labour and confiscating Jewish property.

One hundred Jews, Judenrat members, Jewish Police and key professionals, were exempt and were allowed to live outside the ghetto.

The ghetto was emptied and the remaining inhabitants were transported to Khotinka, a nearby village, and exterminated upon arrival.

In July 1942 the remaining Jews from Rivne (perhaps 7,000 people) were brought by train to Kostopol and were murdered by German police in a quarry near woods outside the town.

Since March 1943, Kostopol was one of locations where Polish civilian population of Volhynia fled from the Ukrainian nationalists (see Volhynian Genocide).