David Conner Treen Sr. (July 16, 1928 – October 29, 2009) was an American politician and attorney from Louisiana. A member of the Republican Party, Treen served as U.S. Representative for Louisiana's 3rd congressional district from 1973 to 1980 and the 51st governor of Louisiana from 1980 to 1984. Treen was the first Republican elected to either office since Reconstruction.

Born in Baton Rouge, Louisiana, on July 16, 1928, Treen grew up in New Orleans and later settled in Metairie. After three unsuccessful runs for Congress in the 1960s, Treen won his first election in 1972 to represent a U.S. House district that covered parts of Greater New Orleans and Acadiana. In Congress, Treen had a reliably conservative voting record, and he subsequently won reelection three times by increasing margins. Treen was among the inaugural members of the House Select Committee on Intelligence when it was created in 1975.

In 1979, Treen won election as governor of Louisiana, and he resigned from the House in 1980 to take office as governor. During his single term as governor, Treen cut the state income tax and created a professional development program for teachers. Treen also signed legislation creating the Louisiana School for Math, Science and the Arts and Louisiana Department of Environmental Quality. However, as the Treen administration took place during the early 1980s recession, Louisiana faced increasing unemployment and bond debt. Treen lost his reelection bid in 1983 to Edwin Edwards, who had served as governor before Treen.

After leaving the governor's office, Treen continued to be politically involved in Louisiana, running for Congress and endorsing gubernatorial candidates as recently as 2008 before his death in 2009.

Treen was born in the state capital of Baton Rouge, Louisiana to Joseph Paul and Elizabeth (née Speir) Treen. He attended public schools in the parishes of East Baton Rouge, Jefferson, and Orleans.

In 1945, Treen graduated from the former Alcee Fortier High School in New Orleans, where his classmates included the subsequent political consultant and journalist Victor Gold. He earned a Bachelor of Arts degree in 1948 in history and political science from Tulane University in New Orleans. While at Tulane, he was a brother of Kappa Sigma fraternity. In 1950, he graduated from Tulane Law School and was admitted to the bar.

Treen served in the U.S. Air Force from 1951 to 1952. After his discharge, Treen joined the law firm of Deutsch, Kerrigan & Stiles. From 1952 to 1957, Treen was legal counsel and vice president of the Simplex Manufacturing Corporation in New Orleans. In 1957, Treen became an associate at the Beard, Blue & Schmitt law firm before eventually being promoted to partner in what became Beard, Blue, Schmitt & Treen.

In the 1960 U.S. presidential election, Treen ran as an elector for the States' Rights Party, which supported Virginia U.S. Senator Harry F. Byrd, Sr., a segregationist Democrat, over the two mainstream candidates, Democrat John F. Kennedy and Republican Richard Nixon. He also served as the chairman of the party's state central committee. Along with Treen, States' Rights electors from Louisiana included hard-line segregationists Leander Perez and Willie Rainach. Treen warned at a rally that "Reconstruction of the South is far from being over" and that "the Democratic and Republican parties would reduce the laboring man to mere tools in a socialistic state."