President Trump has pardoned Stephen E. Buyer, a former Republican representative from Indiana who was convicted of insider trading in 2023.

The pardon for Mr. Buyer was endorsed by current and former Republican lawmakers, including Senators Roger Wicker of Mississippi and Lindsey Graham of South Carolina, and former House Speaker John Boehner, according to the proclamation, which was dated June 4.

Mr. Buyer was sentenced in 2023 to 22 months in prison after being convicted on four counts of securities fraud. The authorities had filed civil and criminal charges against him for trading stock on information about two mergers that he had received from clients of the consulting firm he formed after leaving Congress in 2011, according to the complaint.

Since he returned to the White House last year, Mr. Trump has issued a wave of pardons and commutations. Dozens of pardons have been granted to people accused of white-collar crimes, giving rise to an industry of right-wing operatives hired to bring requests for clemency to the president.

“Mr. Buyer’s career serving as a Judge Advocate General in the United States Army and as a Member of the United States House of Representatives from the State of Indiana was distinguished and highly productive,” Mr. Trump said in the pardon proclamation.

In its complaint against Mr. Buyer, the S.E.C. said that he had learned of T-Mobile’s plan to acquire Sprint from an executive from T-Mobile, one of his clients. Mr. Buyer then purchased $568,000 in Sprint securities, which rose in value by more than $107,000 after the merger became public, the S.E.C. said.

In another deal in 2019, Mr. Buyer learned from one of his clients, the professional services firm Guidehouse, that it would acquire Navigant, a competitor. Mr. Buyer bought more than $1 million of stock in Navigant, which he sold after the acquisition was announced, making a profit of more than $227,000, the S.E.C. said.

Mr. Buyer’s lawyer, Andrew Goldstein, did not immediately respond to a request for comment on Friday night. When the charges were filed in 2022, Mr. Goldstein said that his client was innocent.

Mr. Buyer, 67, was first elected to the House of Representatives in 1992 and announced his retirement from Congress in 2010 to care for his wife, Joni Lynn Buyer, who he said was diagnosed with an autoimmune disease.

In its complaint, the S.E.C. had asked the United States District Court for the Southern District of New York to order Mr. Buyer and his wife to surrender the gains of their trades with interest, and to bar Mr. Buyer from serving as an officer or a director of a company.

Republicans and Democrats in Congress have been grappling with insider trading by lawmakers, who have access to classified information, meet business leaders and set economic policy.

House Republicans have advanced a bill that would impose some restrictions on buying and selling stock by lawmakers and their relatives, though Democrats said the bill contained loopholes that undermined its purpose.