Lt. Gov. David Paterson takes over the governorship, becoming the state's first black and legally blind governor. Spitzer said the resignation is effective Monday at Paterson's request.
"I am deeply sorry I did not live up to what was expected," Spitzer said from his New York office, accompanied at the podium by his wife. "To every New Yorker ... I sincerely apologize."
"As I leave public life, I will do what I need to do to heal." Eventually, he said, he hopes to "serve the common good" outside of politics.
Republican Sen. Joe Bruno, state Senate majority leader, becomes acting lieutenant governor.
Spitzer is allegedly the person identified in court papers as the "Client 9" who paid for a prostitute to travel from New York to Washington Feb. 13 to meet him at a hotel. The court papers, including details of wiretapped conversations, suggested Spitzer was a regular client of the Emperors Club VIP, an escort service.
North Fork Bank's notification to the U.S. Treasury Department's financial crimes network about suspicious activity on one of Spitzer's personal accounts triggered the investigation, The Washington Post reported. The bank's report flagged Spitzer's attempt to structure a $10,000 cash transaction into three parts.
Information about the investigation and Spitzer's link to the high-price prostitution ring came to light Monday. Spitzer has been in seclusion with his family at his New York apartment since then.