Huntsman left the Utah governor's office in 2009, when former President Barack Obama tapped him as ambassador to China.
The posting in Russian Federation was Huntsman's third as ambassador: he also served as ambassador to Singapore from 1992 to 1993 and ambassador to China from 2009 to 2011.
In a resignation letter sent Tuesday morning to President Trump, Huntsman characterized his tenure as a "historically difficult" time in bilateral relations.
Huntsman, 59, was appointed in October 2017.
In November, the envoy revealed that he was battling cancer.
Lawmakers on both sides of the aisle have voiced concerns about Trump's reluctance to impose sanctions on Russia and continued attempts to cast doubt on Russian interference in the 2016 presidential election amid his efforts to improve relations between Washington and Moscow.
President Trump has not personally reacted to Huntsman's exit, but the White House offered this official statement.
Trump reportedly made the call to offer US support for Russian firefighting efforts in Siberia before the discussion turned to Huntsman, the news network said.
He also ran for the GOP's presidential nomination in 2012.
"No reset or restart is going to help, just a clear understanding of our interests and values". Huntsman visited Whelan when he was arrested two weeks after an alleged Russian spy, Maria Butina, pleaded guilty in a USA federal court to trying to influence U.S. "Not much to do in U.S. -Russia relations right now", former U.S. Ambassador to Russia Michael McFaul said in a tweet.
Should he run, Huntsman will face a possibly crowded field that includes Lt. Gov. Spencer Cox, who is polling about the same as Huntsman among registered voters but faring better among Republicans. But your story by THREE reporters @pamelabrown @kyliecnn and Caroline Kelly - not even part of your Moscow bureau - (along with some unnamed embassy source) was disingenuous.
In his two-page letter sent to the White House, Huntsman extolls the work of US diplomats "laboring under extremely hard circumstances to promote and protect America's interests".
In his resignation letter, Huntsman praised the U.S. Embassy staff, saying they had endured "unprecedented expulsions, forced departures and enormous professional disruptions".