Conan Christopher O'Brien (born April 18, 1963) is an Irish American television host and comedian. He is the host of The Tonight Show with Conan O'Brien, a late-night talk show that airs Monday through Friday on NBC. Before The Tonight Show, O'Brien was well-known as the host of Late Night with Conan O'Brien from 1993 to 2009.ref>Associated Press (2008-07-21). "Leno's last 'Tonight' announced". CNN.com. http://www.cnn.com/2008/SHOWBIZ/TV/07/21/tv.nbc.tonight.ap/index.html. Retrieved 2008-07-21. "Leno's last show will be Friday, May 29, and O'Brien will start the following Monday, June 1, NBC executives told a Television Critics Association meeting Monday." </ref> Prior to his hosting career, O'Brien was a writer for Saturday Night Live and the animated series The Simpsons.

O'Brien was born in Brookline, Massachusetts, a suburb of Boston, the son of Ruth (née Reardon), an attorney, and Thomas O'Brien, a physician, epidemiologist and professor of medicine at Harvard. He is the third of six children. O'Brien's family was Irish Catholic and descended from pre-Civil War era immigrants; In a Late Night episode, O'Brien paid a visit to County Kerry, Ireland, where his ancestors originated.

O'Brien attended Brookline High School, where he served as the managing editor of the school newspaper. After graduating as valedictorian in 1981, he entered Harvard University. At Harvard, O'Brien lived in Holworthy Hall during his freshman year, and Mather House during his three upper-class years. He graduated magna cum laude in 1985 with an A.B. in History and Literature. His senior thesis concerned the use of children as symbols in the works of William Faulkner and Flannery O'Connor. Throughout college, O'Brien was a writer for the Harvard Lampoon humor magazine. During his sophomore and junior years, he served as the Lampoon's president. He has been a staunch Democrat since casting his first vote for President in 1984 for Walter Mondale.