Effingham is a town in Carroll County, New Hampshire, United States. At the 2020 census, the town population was 1,691, up from 1,465 at the 2010 census. Effingham includes the villages of Effingham Falls, Effingham, Center Effingham, and South Effingham. Pine River State Forest is in the south.

Carroll County is a county in the U.S. state of New Hampshire. As of the 2020 census, the population was 50,107, making it the third-least populous county in New Hampshire. Its county seat is Ossipee. The county was created in 1840 and organized at Ossipee from towns removed from Strafford County. It was named in honor of Charles Carroll of Carrollton, who had died in 1832, the last surviving signer of the United States Declaration of Independence.