Order 66 may refer to:
- Order 66 (Star Wars), a fictional prearranged military command given by Darth Sidious during the movie Star Wars Episode III: Revenge of the Sith
- Star Wars Republic Commando: Order 66, the fourth novel in the Republic Commando series, written by Karen Traviss
- Order 66/2523, a 1980 anti-communist directive of the Thai government
- Standing Order 66, a 1713 British Parliamentary procedure