According to court documents obtained by ET, Lochte's father, Steven, was one of the witnesses.
Lochte, 33, revealed during the 2016 Summer Olympics that he was dating the 26-year-old former Playboy playmate. He eventually popped the question to Reid in October 2016, and they welcomed a child together, son Caiden Zane, last June.
"Lochte surprised his bride-to-be with a private helicopter tour of Los Angeles, which culminated with a sunset proposal on a Malibu, California, mountaintop overlooking the Pacific Ocean," the athlete's rep told ET at the time. "Lochte proposed with a custom-designed platinum ring featuring a Radiant cut diamond."