The fourth season of the American television comedy series Rules of Engagement premiered as a mid-season entry on March 1, 2010, and concluded on May 24, 2010. It consists of 13 episodes, each running approximately 22 minutes in length. CBS broadcast the fourth season on Mondays at 8:30 pm in the United States between How I Met Your Mother and Two and a Half Men.
<onlyinclude></onlyinclude> Note: The events in episode 1 of season five ("Surro-gate") take place in the immediate aftermath of the events in episode 10 of season four ("The Surrogate"), with the events in episodes 11, 12 and 13 of season four taking place outside of the story line of "The Surrogate" and "Surro-gate."