"Whatever skills I may have are better utilized in a courtroom than in Congress, and I enjoy our justice system more than our political system," Gowdy said in a statement. "As I look back on my career, it is the jobs that both seek and reward fairness that are most rewarding."
The special panel's discovery of Clinton's use of a private email server for government business became a significant issue in the 2016 presidential campaign, in which she was the Democratic nominee, and prompted an FBI review of her actions that reverberated until the final days of the race.
Gowdy's district, in northern South Carolina, is heavily Republican.
More than 40 House Republicans have decided to step down this cycle. Some received jobs in the Trump administration; others are leaving to seek higher office or because they were accused of sexual misconduct or harassment. Still others faced tough reelection campaigns or blamed the divisive political climate.
It was unclear what role Gowdy might seek in the justice system. One of the judges on the U.S. Court of Appeals for the 4th Circuit took "senior status" Tuesday, creating a vacancy on the bench.
Gowdy, who won his seat in 2010 by ousting moderate Republican Bob Inglis, had talked for years about retiring. In 2016, he waited until weeks before the election filing deadline to declare his candidacy for reelection, after months of speculation that he would leave once the House Select Committee on Benghazi finished its work.
"Some friends of Trey Gowdy need [to] talk him out of retiring," Sen. Charles E. Grassley (R-Iowa) tweeted Wednesday. "America needs a smart forceful congressman like him."
Gowdy's contribution to the Benghazi panel made him a major player in the 2016 election. His researchers discovered that Clinton had used a private server for email while in the State Department, and in 2015, weeks before the first votes were cast in the Democratic presidential primaries, Gowdy brought Clinton before the committee for testimony that dragged late into the night.
Gowdy's background as a prosecutor was legendary among his colleagues, who praised him for asking precise, cutting questions in settings where members of Congress were often given to rambling.
"He can ask a question," Sen. Lindsey O. Graham (R-S.C.) said when Gowdy was picked to run the committee, adding, "Now, the bar is low in Congress — I'll be first to admit."
In 2017, after then-Oversight Committee Chairman Jason Chaffetz (R-Utah) surprised Republican House members by retiring from Congress, Gowdy's colleagues chose him to lead that panel. In that role, Gowdy emerged as a defender of President Trump in the ongoing investigations of Russian involvement in the 2016 presidential campaign, most recently saying that text messages between FBI agents who were looking into Trump's campaign suggested that their investigation was biased.
In another retirement, an 11-term congressman, Rep. Robert A. Brady (D-Pa.), announced he will not run for reelection, ending a long career in Philadelphia politics after being embroiled in scandal over an alleged payoff to a would-be challenger.
"Today, I'm choosing family over service," Brady, 72, said at a news conference.
In October, two of Brady's consultants — Donald Jones and Ken Smukler — were indicted as part of an investigation into a $90,000 payment that Brady's 2012 campaign made to challenger Jimmie Moore. The FBI's probe ensnared Brady, though the congressman professed his innocence, even after Jones pleaded guilty last month to making false statements about the payoff.