As chairman, he made online privacy protection one of his top priorities. He settled charges with Facebook, Google and other Web companies for failing to follow their own privacy policies.
The agency also expanded regulations aimed at protecting the online privacy of children.
Earlier this month, the FTC closed its sweeping antitrust investigation into Google's search practices. The agency decided to take no action against Google over allegations that it manipulates its search results to boost its own services.
In announcing the decision, Leibowitz acknowledged that Google's search results may hurt competitors, but he concluded that the primary reason the company made changes to its search algorithm was to improve the experience for users.
Some of the lead contenders for the chairman's role are the FTC's two Democratic commissioners, Julie Brill and Edith Ramirez.
Antitrust lawyers had been saying for months that they expected Leibowitz to step down sometime after the election and head to the private sector. In Friday's announcement, Leibowitz did not mention if he has decided where he will go next.
Before serving on the FTC, Leibowitz was the vice president of congressional affairs for the Motion Picture Association of America. Before that, he had a long career on Capitol Hill, including time as the chief counsel for the Senate subcommittee on antitrust issues.
He is married to Washington Post columnist Ruth Marcus and has two daughters.