The attorney general is recused from that investigation, but could be a key witness to the events under scrutiny. In 2016, he met at least twice with Russian Ambassador Sergey Kislyak. After Trump was elected, Sessions was one of a small number of administration officials involved in discussions with the president that led to the firing of FBI Director James B. Comey in May, at a time when Comey was overseeing the Russia probe.
Sessions's lawyer, Chuck Cooper, who was with him during the interview, declined to comment.
The interview, the first known instance of a Cabinet official being interviewed in the Mueller investigation, was first reported by the New York Times. Months ago, the special counsel's office also interviewed Comey, but that conversation was described as brief, involving Comey vouching for the contents of memos he wrote about private conversations with the president, according to people familiar with the matter.
Sessions's role in the investigation and his supervision of the Justice Department have been marked by controversy.
Sessions's decision to recuse himself from matters related to the 2016 election campaign has greatly angered Trump. Some conservative lawmakers have called for Sessions to resign, arguing he has not reined in what they call a reckless FBI investigation of the president.
At times, the attorney general has struggled to explain what was said in private meetings that are now of interest to investigators.
During his confirmation hearing in early 2017, Sessions was asked what he would do if he learned there had been contacts between Russians and the Trump campaign, and he answered: "I did not have communications with the Russians.''
After The Washington Post reported that he met at least twice with Kislyak in 2016, Sessions announced he was recusing himself from investigations involving the election, based on the advice of Justice Department ethics lawyers.
He has since maintained that he misunderstood the scope of the question at his confirmation hearing, and that his meetings with Kislyak were fleeting or strictly in his capacity as a U.S. senator. In announcing his recusal, Sessions said: "I never had meetings with Russian operatives or Russian intermediaries about the Trump campaign."
That assertion is contradicted by the accounts Kislyak provided to his superiors in Moscow, according to current and former U.S. officials.
Kislyak reported to his bosses that he discussed campaign-related matters, including policy issues important to Moscow, with Sessions during the 2016 presidential race.
At the time, Sessions was a top foreign policy adviser to Trump the candidate. Kislyak's account of the conversations were intercepted by U.S. spy agencies, who regularly monitor the communications of senior Russian officials in the U.S. and Russia.
One U.S. official said that Sessions has provided "misleading" statements that are "contradicted by other evidence." A former official said that the intelligence indicates that Sessions and Kislyak had "substantive" discussions on matters including Trump's positions on Russia-related issues and prospects for U.S.-Russia relations in a Trump administration.
Sessions's recusal from the Russia probe has continued to rankle the president, according to administration officials, and the attorney general has become embroiled in other internal battles in recent months.
In December, Sessions pushed FBI Director Christopher A. Wray to remove and replace some of his top aides, particularly Deputy Director Andrew McCabe. Trump and others have argued those top aides, who served at the FBI under Comey, are biased against the president.