Koch led his city for 12 years, with a brash, humor-tinged style that came to personify the New York of the 1980s.
The Democratic mayor is credited with helping save New York from its economic crisis in the 1970s and leading it to financial rebirth. But during his three terms as mayor, he also faced racial tensions and corruption among political allies, as well as the AIDS epidemic, homelessness and urban crime.
In his weekly radio address, Bloomberg called Koch "our most tireless, fearless, and guileless civic crusader."
The mayor said his predecessor's "tough, determined leadership and responsible fiscal stewardship <t40>...<t$> helped lift the city out of its darkest days and set it on course for an incredible comeback."
He added, "When someone needed a good kick in the rear, he gave it to them."
Koch lost the Democratic nomination for mayor in 1989 to David Dinkins, who succeeded him.
Koch said he was defeated "because of longevity." In his words, "people get tired of you."
But as the votes were coming in, he said he told himself, "I'm free at last."
Also Monday, U.S. Rep. Carolyn Maloney will announce the renaming of a Manhattan subway station in Koch's honor.
The subway station at East 77th Street and Lexington Avenue will be called "Mayor Ed Koch subway station," according to Maloney.
City officials have introduced legislation to officially rename the station.