Griner asked Johnson to marry her Thursday night and posted a photo of the proposal Friday on Instagram.
"Last Night was a Night to Remember ... I became the happiest person on this earth! (almost pass out but when that one word came out I came back to life) Me and my baby @missvol25 are in it for Life!," Griner wrote in the caption along with the photo.
Johnson also used the social media platform to tell the world about the big news and show off her diamond-encrusted ring.
"What I get to wake up to ... @brittneygriner#LoveMakesYouDoTheCraziestThings," she wrote in the caption.
Griner made headlines regarding her sexuality earlier this year when she said Baylor coach Kim Mulkey urged her to keep quiet about being a lesbian.