The 50-year-old representative and chairman of the State House Committee on Oversight and Government Reform said after "long consultation with my family and prayerful consideration," he will "return to the private sector." He said the decision had nothing to do with his health or fear of losing re-election.
"After more than 1,500 nights away from my home, it is time," Chaffetz wrote in the post. "I may run again for public office, but not in 2018."
Utah's next gubernatorial race will be held in 2020.
Shortly after Chaffetz made his announcement, speculation about who would take his place erupted.
Lt. Governor Spencer J. Cox said on Twitter it is "far too soon to be speculating about a 2020 governor race," but said he and his family will discuss the matter when "the time is right."
Dr. Kathryn Allen, who raised money to run against Chaffetz after his notorious iPhone comment, told 2News she was "shocked" by the announcement. She said she "thinks there is something going on that we don't know."
As for her campaign, Allen said she is "encouraged" by what she sees in Georgia.
"I think we might be a swing district now and that would be awesome if we got national attention," she said. "I think that most people will view this as an opportunity for a real change in their district, and I think I will get even more support."
2News has also learned that Provo Mayor John Curtis is considering running for Congress.
Buzzfeed reported the story first, citing two unnamed sources "who have been informed of his decision." Chaffetz later posted an announcement on his Facebook page.
Chaffetz, a Republican, was first elected in 2008. He has served as chairman of the Oversight Committee since 2015.
See a list of reactions, both positive and negative, to Chaffetz' announcement here.