Lunar Base 3 was a Starfleet operated base located on Earth's moon.
In 2375, Lunar Base 3 launched runabouts during the Breen attack on San Francisco to distract the Breen warships while the USS Enterprise-E freed the USS Columbia from Starbase 1. The runabouts were fired on by DP-7, which was under Breen control, leaving them lifeless. (TNG - Tales of the Dominion War short story: "Eleven Hours Out")