The Secret Six is a name that has been used by several groups in the DC Universe. The original version was a group of adventurers blackmailed into working together by their mysterious leader, the Mockingbird. Villains United introduced a new version of this group that consisted entirely of super-villains. This group was put together by Lex Luthor posing as the Mockingbird to take down the Secret Society of Super-Villains, and they used the House of Secrets as their base.

The original Secret Six was created by E. Nelson Bridwell and Frank Springer, first appearing in Secret Six #1 (1968). The super-villain group was created by Gail Simone, first appearing in Villains United #1 (2005). An earlier version of the group predating the other two versions appeared in Doll Man #36 (1951).