Dillon is a city in and the county seat of Beaverhead County, Montana, United States. The population was 3,752 at the 2000 census.
Dillon is located at 45°12′57″N 112°38′3″W / 45.21583°N 112.63417°W / 45.21583; -112.63417 (45.215735, -112.634055), at an altitude of 5102 feet (1555 m). It lies approximately 40 miles (65 km) east of the Continental Divide.
According to the United States Census Bureau, the city has a total area of 1.6 square miles (4.2 km²), all of it land.