| Kosów Lacki | |
| Pushpin Map: | Poland |
| Pushpin Label Position: | bottom |
| Subdivision Type: | Country |
| Subdivision Type1: | Voivodeship |
| Subdivision Name1: | Masovian |
| Subdivision Type2: | County |
| Subdivision Name2: | Sokołów |
| Subdivision Type3: | Gmina |
| Subdivision Name3: | Kosów Lacki |
| Leader Title: | Mayor |
| Leader Name: | Stanisław Słomiak |
| Established Title: | Established |
| Established Date: | 13th century |
| Established Title3: | Town rights |
| Established Date3: | 1723–1869, 2000 |
| Area Total Km2: | 11.57 |
| Population As Of: | 2006 |
| Population Total: | 2135 |
| Population Density Km2: | auto |
| Timezone: | CET |
| Utc Offset: | +1 |
| Timezone Dst: | CEST |
| Utc Offset Dst: | +2 |
| Coordinates: | 52.6°N 31°W |
| Postal Code Type: | Postal code |
| Postal Code: | 08-330 |
| Area Code: | +48 25 |
| Blank Name: | Car plates |
| Blank Info: | WSK |
| Website: | http://www.kosowlacki.pl |
Kosów Lacki is a town in Sokołów County, Masovian Voivodeship, Poland, with 2,152 inhabitants (2004).
Within the municipal territory are the two Treblinka camps.