Oklahoma athletic director Joe Castiglione will retire from his full-time role during the upcoming school year, the school announced Monday.

Castiglione's retirement will mark the end of the longest run for an active athletic director in major college sports, according to ESPN's Pete Thamel. He will hold the title of athletic director emeritus once a successor is found. This will allow Castiglione to continue to work on "special projects," Thamel adds.

Castiglione is entering his 28th year as Oklahoma's athletic director. He first took the job in 1998, and the program has won 26 national titles since then.

The Sooners' football program won the national championship during Castiglione's tenure in 2000. The program also made the switch from the Big 12 to SEC under his watch.

Castiglione's first athletic director job was at Missouri from 1994-98.