Lamar
- County:
- Barton County
- County Seat:
- Yes
- Area (mi²):
- 5.214
- State:
- Missouri
Lamar is a city located in Barton County, Missouri. Lamar has a 2026 population of 4,299. It is also the county seat of Barton County. Lamar is currently declining at a rate of -0.14% annually but its population has increased by 0.82% since the most recent census, which recorded a population of 4,264 in 2020.