Rudolph W. Giuliani — the former mayor of New York, top federal prosecutor and a longtime ally of former President Donald J. Trump — has been disbarred from the practice of law effective immediately, a New York State appellate court ruled on Tuesday.

The ruling continued the downfall of a disgraced lawyer who once portrayed himself as a crusader for law and order, challenged mob bosses and Wall Street operators and, after the Sept. 11 terror attacks, became, for many, a national hero.

Mr. Giuliani, 80, has filed for bankruptcy, faces indictment in Arizona and Georgia in election cases and owes $148 million to two Georgia election workers stemming from a judgment in a defamation lawsuit.

The 31-page order disbarring Mr. Giuliani from practicing law in New York focused on his work as the personal lawyer for Mr. Trump and his 2020 presidential campaign. It said Mr. Giuliani was being disciplined for lies he told in numerous forums that were “designed to create distrust of the elective system of our country in the minds of the citizens and to destroy their confidence in the legitimacy of our government.”