Kosów Lacki
Church of the Nativity of the Virgin Mary
Coat of arms
Kosów Lacki
Coordinates: 52°36′N 22°9′E / 52.600°N 22.150°E / 52.600; 22.150
Country	Poland
Voivodeship	Masovian
County	Sokołów
Gmina	Kosów Lacki
Established	13th century
Town rights	1723–1869, 2000
Government
• Mayor	Stanisław Słomiak
Area
• Total	11.57 km2 (4.47 sq mi)
Population  (2006)
• Total	2,135
• Density	180/km2 (480/sq mi)
Time zone	UTC+1 (CET)
• Summer (DST)	UTC+2 (CEST)
Postal code	08-330
Area code	+48 25
Car plates	WSK
Website	http://www.kosowlacki.pl

Kosów Lacki [ˈkɔsuf ˈlat͡skʲi] is a town in Sokołów County, Masovian Voivodeship, Poland, with 2,152 inhabitants (2004).

Within the municipal territory are the two Treblinka camps.

• 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 Francis in ecstasy [es]" was found in the presbytery in Kosów Lacki.
• 01.01.2000 - Restoration of civic rights.

• Official town and commune webpage
• The diocesan museum in Siedlce (when is a El Greco picture ) webpage^{[permanent dead link]}
• Jewish Community in Kosów Lacki on Virtual Shtetl