Huntsman sent his resignation letter to President Donald Trump on Tuesday, to take effect on 3 October.
The 59-year-old previously served as Utah governor from 2005 to 2009.
His first ambassadorial duty was from 1992 to 1993 when he served as the U.S. envoy to Singapore.
In Huntsman’s resignation letter shared by the Tribune, he wrote that “we must continue to hold Russia accountable when its behavior threatens us and our allies.”
President Trump has previously faced criticism for his administrations relationship with Russia, including allegations that Moscow interfered with the U.S. presidential elections in 2016.
Trump said he believed Russia’s denial of any interference in the vote.
If he runs for governor, Huntman will face Lt. Gov. Spencer Cox in the Republican primary.