Lamar Township is a township in Clinton County, Pennsylvania, United States. The population was 2,450 at the 2000 census.
According to the United States Census Bureau, the township has a total area of 41.0 square miles (106.2 km²), of which, 41.0 square miles (106.1 km²) of it is land and 0.04 square miles (0.1 km²) of it (0.07%) is water.
As of the census of 2000, there were 2,450 people, 901 households, and 718 families residing in the township. The population density was 59.8 people per square mile (23.1/km²). There were 967 housing units at an average density of 23.6/sq mi (9.1/km²). The racial makeup of the township was 99.10% White, 0.16% African American, 0.12% Native American, 0.16% Asian, and 0.45% from two or more races. Hispanic or Latino of any race were 0.37% of the population.