Doonesbury is a comic strip by American cartoonist Garry Trudeau that chronicles the adventures and lives of an array of characters of various ages, professions, and backgrounds, from the President of the United States to the title character, Mike Doonesbury, who has progressed over the decades from a college student to a youthful senior citizen.

Created in "the throes of '60s and '70s counterculture", and frequently political in nature, Doonesbury features characters representing a range of affiliations, but the cartoon is noted for a liberal viewpoint. The name "Doonesbury" is a combination of the word doone (American prep school slang for someone who is clueless, inattentive, or careless) and the surname of Charles Pillsbury, Trudeau's roommate at Yale University.

Doonesbury is written and penciled by Garry Trudeau, then inked and lettered by an assistant, Don Carlton, then Todd Pound. Sunday strips are colored by George Corsillo. Doonesbury was a daily strip through most of its existence, but since February 2014 it has run repeat strips Monday through Saturday, and new strips on Sunday.

Doonesbury began as a continuation of Bull Tales, which appeared in the Yale University student newspaper, the Yale Daily News, from 1968 to 1970. It focused on local campus events at Yale.

Doonesbury proper debuted as a daily strip in twenty-eight newspapers on October 26, 1970 (it being the first strip from Universal Press Syndicate). ^{[failed verification]} A Sunday strip began on March 21, 1971. Many of the early strips were reprints of the Bull Tales cartoons, with some changes to the drawings and plots. B. D.'s helmet changed from having a "Y" (for Yale) to a star (for the fictional Walden College). Mike and B. D. started Doonesbury as roommates; they were not roommates in Bull Tales.

Doonesbury became known for its social and political commentary. By the 2010s, it was syndicated in approximately 1,400 newspapers worldwide.

In May 1975, Doonesbury became the first daily comic strip to win a Pulitzer Prize, taking the award for Editorial Cartooning. That year, U.S. President Gerald Ford told the Radio and Television Correspondents' Association at their annual dinner, "There are only three major vehicles to keep us informed as to what is going on in Washington: the electronic media, the print media, and Doonesbury, not necessarily in that order."

Trudeau took a 22-month hiatus, from January 2, 1983, to September 30, 1984. Before the break in the strip, the characters were eternal college students, living in a commune together near Walden College, which was modeled after Trudeau's alma mater, Yale. During the break, Trudeau helped create a Broadway musical of the strip, showing the graduation of the main characters. The Broadway adaptation opened at the Biltmore Theatre on November 21, 1983, and played 104 performances. Elizabeth Swados composed the music for Trudeau's book and lyrics.