Altona is an unincorporated community and a census-designated place (CDP) located in and governed by Boulder County, Colorado, United States.

[5] The Altona, Colorado, post office operated from October 2, 1879, until July 15, 1916.

[6] Altona is located in central Boulder County where Left Hand Creek exits the Front Range of the Colorado Rockies.

U.S. Highway 36 passes through the community, leading north to Lyons and south to Boulder.

Altona is 10 miles (16 km) west of Longmont by Nelson Road.