Rep. Ralph M. Hall, 90, is pledging to retire after his next term ends in January 2017, reports The Rockwall Herald-Banner.
The Texas Republican, first elected to the House in 1980, faces a primary challenge against five Republicans, but is expected to win.
"I have had the privilege of serving the people of Rockwall and East Texas for some time," he said in Rockwall, per the paper. "I look forward to campaigning for re-election the next couple of months and serving one final term in Congress."
Hall in December 2012 became the oldest member ever to serve in the House. He is three years ahead of Rep. John Dingell (D-Mich.), who was first elected in a December 1955 special election. Seven other House members are in the 80s.
But Hall isn't even close to becoming the oldest member to serve in Congress. Sen. Strom Thurmond served until just past his 100th birthday. The South Carolina Republican finally retired in January 2003 - and died six months later.
Sen. Dianne Feinstein is the oldest senator, at age 80. The California Democrat is just a few months ahead of Sen. Charles Grassley (R-Iowa). And 22 senators are in their 70s.
Like many other Lone Star State conservatives Hall was originally a Democrat. In fact, he served his first 23 years in Congress as a Democrat - the first 14 in the majority, the next nine in the minority.
When Hall finally joined the Republicans, in January 2004, the GOP leadership rewarded him with the chairmanship of the Energy and Air Quality Subcommittee of the Energy and Commerce Committee. Hall helped to enact the energy bill of 2005 and later fought Democratic proposals to raise taxes on oil companies.