The appointment will be effective no later than July 1, said MSU President Robert H. "Doc" Foglesong, who announced the selection following a six-month search that began last August.
"We promised to move expeditiously to fill this position with the best candidate possible, and with Greg we have done that," he said. "He brings both experience and respect to his new role at Mississippi State."
Longtime athletic director Larry Templeton, who has served since 1987 in the position, will become a special assistant to Foglesong until no later than June 30.
"Larry Templeton has spent his life committed to Mississippi State University, and we wish him well as he finally gets a chance to relax and step into the next phase of his life," said Foglesong.
He said he expects a seamless transition as Byrne moves into his new role.
"We're incredibly blessed to have Greg Byrne step into this position," he said. "He has been deeply engaged in MSU for the last two years, and he brought me a strategic plan that will enable us to move to the next level in athletics."
Foglesong added: "He comes from an athletic family, but he brings his own fresh ideas at a time when Mississippi State is making a new start in its athletics programs."
Byrne's father, Bill, is the athletics director at Texas A&M.
Greg Byrne has spent more than 15 years in intercollegiate athletics, serving prior to his MSU position as associate director of athletics for fund-raising and development at the University of Kentucky and in a similar role at Oregon State University.
He holds a bachelor's degree from Arizona State University and is expected to receive a master's from Mississippi State by the end of 2008.
"This is an incredible leadership opportunity at a university that has incredible potential," Byrne said. "I'm looking forward to the challenges and to the future of Mississippi State's athletic programs."