Rudy Giuliani is the subject of a federal probe into whether he broke lobbying laws in his dealings with Ukraine, according to a new report.

Investigators are scrutinizing Giuliani’s efforts to undermine the work of the former US ambassador to Ukraine, Marie Yovanovitch, one source familiar with the probe told The New York Times on Friday evening.

The investigation is being conducted by prosecutors in the Southern District of New York — the same district where Giuliani served as US Attorney before becoming mayor of New York in 1994.

ABC News on Friday  also reported that Giuliani was the subject of an SDNY investigation, though they described the probe in less specific terms, saying it involved the business relationship between the former mayor, Trump and two Soviet-born businessmen.

The businessmen, Lev Parnas and Igor Fruman, are accused of helping Giuliani dig for dirt on Joe Biden, and were arrested by the feds in New York  on charges they funneled foreign cash to Republican politicians to advance their interests and those of a Ukrainian official who wanted then-US Ambassador Marie Yovanovitch fired.

Giuliani had not commented on news of the probe as of early Saturday morning, and did not immediately respond to a request for comment by The Post.

He told Fox News Friday that Parnas and Fruman “logistically helped” him collect evidence against Hunter Biden and connected him with two former Ukrainian prosecutors — but called the timing of their arrest “suspect” and said he would “reveal relevant facts very, very shortly.”

Trump appeared to distance himself from Giuliani Friday night, saying, “I don’t know. I haven’t spoken to Rudy,” when asked by reporters if the ex-mayor was still his personal attorney.

Giuliani later told The Washington Post that he was still the president’s lawyer.

The Florida-based businessmen were nabbed at Dulles International Airport in Virginia with one-way tickets to Vienna.

They have been named as witnesses in the ongoing impeachment inquiry into Trump and have been subpoenaed to testify before several House committees.