Kosów Lacki [ˈkɔsuf ˈlat͡skʲi] is a town in Sokołów County, Masovian Voivodeship, Poland, with 2,152 inhabitants (2004).
- 1202 - First mention of a village Kossów found in documents belonging to prince Konrad Mazowiecki.
- 1723 - A permit was granted to organize a market twice a week and a fair four times in a year. Kosów was established as a town.
- 18th century - There were two schools in Kossów, in which 40 percent of the students were girls.
- 1869 - Civic rights were canceled, because Kosów participated in The January Uprising.
- 1964 - A picture by El Greco titled "Saint Francise ecstasy" was found in the presbytery in Kosów Lacki.
- 01.01.2000 - Restoration of civic rights.
Coordinates: 52°36′N 22°09′E / 52.600°N 22.150°E