Flanked by his wife, Spitzer told a press conference in his Manhattan office that he will leave public life.
"I am deeply sorry that I did not live up to what was expected of me. To every New Yorker, to those who believed in what I tried to stand for, I sincerely apologize."
"The remorse I fell will always be with me," Spitzer said, "Words cannot describe how grateful I am for the love and compassion they have shown me."
Lt. Gov. David Paterson will finish out Spitzer's term, which ends in 2010.
The Brooklyn-born Paterson was first elected to represent Harlem in the State Senate in 1985 and became Senate minority leader in 2002.
Spitzer, a former state attorney general who made his reputation as a law-and-order reformer, was barely a year into his first term as governor.
A rising star in the Democratic Party, he was once touted as a possible future presidential candidate.
New York Governor Eliot Spitzer announces his resignation at his office in New York, March 12, 2008. (Xinhua/Reuters Photo)