The fourth season of the American television comedy series How I Met Your Mother premiered on September 22, 2008 and concluded on May 18, 2009. It consisted of 24 episodes, each running approximately 22 minutes in length. CBS broadcast the fourth season on Monday nights at 8:30 pm in the United States. The complete fourth season was released on Region 1 DVD on September 29, 2009. In the United Kingdom it began airing via E4 from Thursday, December 10 weekly.
To date, it is the only season of the series to be nominated for the Primetime Emmy Award for Outstanding Comedy Series.