The singer announced the news Thursday on Instagram before the song debuted at midnight.
"Gwen and I decided we were going to write our own vows for the wedding, but I decided to surprise her by writing a song instead…" he captioned a photo of the couple on their wedding day.
Stefani quickly reposted the news on her own account, gushing the song was the "most amazing beautiful gift i ever received." The proud wife followed her caption with multiple hashtags, including #amazingperson.
TODAY's Carson Daly, who also hosts "The Voice," officiated the couple's summer nuptials. He weighed in on the exciting announcement.
"You didn’t decide to! I forced you to," Carson commented. "Thank Jesus too, yielded the best wedding moment & a hit song! You should buy me a tracker w the royalties cowboy."
The song details the love between the musical superstars.
"And I know we can reach the stars, That's how far my love will go for you," Shelton sings in the ballad. "I know we can reach the stars, You've already hung the moon."
Shelton, 45, and Stefani, 52, met in 2014 as coaches on "The Voice" and tied the knot in a small ceremony in front of immediate family and friends on Shelton's Oklahoma property this summer.
The release of the song, which Shelton co-wrote with songwriter Craig Wiseman, has been a long time in the making.
"I want people to hear it," Shelton said during an October appearance on "Late Night with Seth Myers."
"I mean, my god, I married Gwen Stefani," he quipped. "I want everybody to hear that. I mean, that's the ultimate bragging rights."
Shelton has plans to include the track on the deluxe version of his album, "Body Language", which is set to release on Dec. 3.