Galloway, a fifth-year senior from Dallas, was expected to be one of three returning starting offensive linemen for the Cowboys this season. Last year, he blocked for star tailback Chuba Hubbard, who led the FBS with 2,094 rushing yards.
Galloway told Sports Illustrated in a text message on Wednesday night: "I'm done with football. I was getting hurt so much and I felt like all of my injuries were piling up to where they were effecting me too much on and off the field."
Sources confirmed to ESPN that Galloway has retired.
Hubbard, 6-foot-5 and 326 pounds, battled shoulder injuries in each of the previous two seasons and missed four games because of an ankle injury in 2019.
The Cowboys are expected to bring back starting right tackle Teven Jenkins and right guard Bryce Bray, as well as West Virginia transfer Josh Sills, who started two seasons at guard for the Mountaineers. Center Ry Schneider and guard Hunter Anthony also have starting experience.
The Cowboys are scheduled to open the season against Oregon State at home on Sept. 3.