G.I. Joe: Sigma 6 is a line of military-themed action figures and toys produced by Hasbro, re-imagining the characters of the 1980s toyline, G.I. Joe: A Real American Hero.

The Sigma 6 toy line served several purposes for Hasbro. First, it allowed them to depart from the classic 3 ¾-inch format of the A Real American Hero series of the 1980s; most Sigma 6 action figures stand at approximately 8 inches (200 mm) and have more articulation. Second, the new series offered them the chance to streamline the story and characters, stripping away old continuity and "rebooting" the franchise with younger versions of the cast, rendered in the anime style.

The line proved to be polarizing with G.I. Joe fans and ultimately unsuccessful at retail. Sigma 6 was cancelled after two years leaving many showcased sets and characters unproduced. In 2007 Hasbro went back to the classic 3¾”- 4” scale for the 25th anniversary line and beyond.