The Eureka Stockade Flag, used as the flag of the Builders Labourers' Federation

The Builder's Labourers Federation (BLF) was an Australian trade union organisation which operated from 1911 until 1972. It briefly resumed operation from 1976 until 1986 and was then deregistered permanently in some Australian States. The BLF currently exists as the state section of the Construction division of the Construction, Forestry, Mining and Energy Union , however, these state sections were never part of the radical, militant BLF that most people remember. The BLF fought successful campaigns blocking developments by imposing "green bans " which they claimed did not preserve the heritage of Sydney or otherwise impacted the environment adversely. These included the blocking of plans to develop Centennial Park to make way for the Olympics in the 1980s.

The union's slogan was Dare to struggle, Dare to win.