Before she was arrested and deported, Russian spy Anna Chapman was living with powerhouse New York lawyer John Altorelli, who told friends she gave him the “best sex” he ever had.

According to sources, the legal eagle and the sexy spy shacked up in his West 37th Street apartment. He threw a party there with Chapman in June 2010, just before her arrest, where he introduced her to friends as “the woman in his life.” Altorelli also boasted to pals that Chapman was very adventurous in bed.

It’s unclear when the relationship began, but sources tell Page Six that Altorelli caught Chapman’s eye after he separated from his wife and shed a lot of weight. They add that he showered Chapman with gifts, including clothes and jewels, and they cohabitated in his huge Hell’s Kitchen apartment.

There’s still a picture of them together on the Web site of society fotog Patrick McMullan, dated May, 18, 2010. Sources said that Chapman’s Facebook page, since taken down, was plastered with pictures of the pair. The McMullan shot shows them posing with other guests at an FDNY dinner at the Hilton.

Altorelli was not suspected of knowing about Chapman’s secret life as a spy.

Sources say that when Chapman first got into hot water with the law, she told him she was “having problems with her visa.”

Altorelli this month made a high-profile move from the firm Dewey & LeBoeuf, where he was a partner, to DLA Piper, which bills itself as the nation’s largest law firm. He’s now co-chairman of DLA Piper’s US finance practice and a member of the executive committee.

When we called Altorelli he told us, “I know why you are calling.” But when we asked about Chapman he said, “No comment.”

Chapman was deported in July 2010 on suspicion of working for a Russian spy ring and pleaded guilty to conspiracy to act as an agent of a foreign government without notifying the US attorney general.