Four Square Mile is an unincorporated community and a census-designated place (CDP) located in and governed by Arapahoe County, Colorado, United States.

The CDP is surrounded by Denver on the north, west, and south and by Aurora on the east.

Annexation of the Arapahoe County enclave was contested between Denver and Aurora in the early 1970s, with Denver annexing east from Quebec Street and Aurora west from Havana Street.

[5] Denver’s annexations were ultimately stopped by the Poundstone Amendment; Aurora is not similarly limited but made its most recent annexation to Dayton Street in 1984, leaving nearly three of the four square miles unincorporated.

The Four Square Mile CDP includes Sullivan, a previous unincorporated community designation.