Stephen K. Bannon, the longtime ally of former President Donald J. Trump, will have to report to federal prison on Monday after the Supreme Court rejected his final effort to stave off a four-month sentence for contempt of Congress.

In a single-sentence decision issued on Friday, the court rejected Mr. Bannon’s request to remain free while he challenges his conviction on charges of defying a subpoena from the House committee that investigated the Jan. 6, 2021, attack on the Capitol. Mr. Bannon had filed a last-ditch petition to Chief Justice John G. Roberts Jr. last week, asking for permission to hold off on surrendering to the authorities.

In July 2022, Mr. Bannon was found guilty at a trial in Washington of ignoring the subpoena, which sought information about his role in the events of Jan. 6. Even though he was sentenced to four months in prison, he was initially allowed to remain free while he pursued a lengthy appeals process.

Last month, however, a federal appeals court upheld his contempt conviction and within a few weeks the judge overseeing his case, Carl J. Nichols, said he would have to start serving his time.

In their petition to Justice Roberts, Mr. Bannon’s lawyers said that if he was forced to report to prison next week, he would almost certainly serve his entire sentence before he could ask the full Supreme Court to hear his appeal of his guilty verdict. The court’s current term ends on Monday and Mr. Bannon is not expected to be released until just before the election in November.

CNN reported this month that Mr. Bannon would serve his sentence at a low-security federal prison in Danbury, Conn. A lawyer for Mr. Bannon did not respond to requests for comment.

Mr. Bannon is likely to remain in custody even as he goes on trial in Manhattan in a separate case, in which he stands accused of misusing money he had helped raise for a group backing Mr. Trump’s attempts to build a wall on the southern border.

That trial is scheduled to begin later this year, in the same state courthouse where Mr. Trump was convicted on charges of falsifying business records to cover up a sex scandal that threatened his 2016 run for the presidency.

Mr. Bannon will become the second former aide to Mr. Trump to be jailed for failing to comply with a subpoena from the Jan. 6 committee. Peter Navarro, who advised Mr. Trump on trade issues, is approaching the end of his own four-month term in a federal prison in Miami.

The House panel had wanted to question Mr. Bannon and Mr. Navarro about their efforts to coordinate with Republican members of Congress to challenge the results of the election on Jan. 6. The committee members also wanted to ask Mr. Bannon about remarks he had made on his podcast, “War Room,” on Jan. 5, 2021, saying that “all hell was going to break loose” the following day.

But Mr. Bannon ignored the committee’s requests, and the House found him in contempt in October 2021. Almost a year later, when prosecutors took him to trial, he sought to defend himself by blaming his lawyer for advising him to defy the panel.