Sheriff Billy Long resigned his post on Wednesday, citing his current "legal predicament."
Long, who is facing a variety of federal charges, said he was doing so effective immediately.
In a letter delivered by attorney Jerry Summers, he apologized and said he is sorry for his actions.
County Commission Chairman Bill Hullander said the commission will be taking applications for an interim sheriff.
He said Chief Allen Branum is currently in charge of the department.
The County Commission will meet on Thursday at 9:30 a.m. to begin the process of choosing the replacement.
There is a seven-day notice period in regard to the vacancy.
There will be an election in August to complete the Long term.
Chairman Hullander said the commission will discuss whether they would want the interim to agree not to run in August. He said he personally had no problem with the interim running.
Chairman Hullander, who said he spoke with the former sheriff for about two minutes on Tuesday, said he is glad there did not have to be an ouster procedure. He said he told Long he was praying for him and his family.
The Long letter says, "As a result of my legal predicament, I cannot fulfill my obligations as sheriff of Hamilton County, Tennessee, and therefore I tender my resignation from said position effective immediately.
"I wish to publicly apologize to the citizens and voters of Hamilton County, the officers and employees of the Hamilton County Sheriff's Department, my family, friends and supporters for any embarrassment that I may have caused them.
"I humbly ask for your prayers and support for the officers in law enforcement in Hamilton County who protect our citizens on a daily basis."
He is due in Federal Court on Friday at 2 p.m. for a detainment hearing on charges of bribery, money laundering, providing a gun to a felon, and possession of cocaine for resale.
Chief Branum, former police chief in Soddy-Daisy, said he will submit his name for interim sheriff.
Former Sheriff John Cupp has said he would serve as interim if asked by the commission, but he said he would not be a candidate in August.
Rep. Vince Dean of East Ridge has said he may run for the post in August.
John Bailes, chairman of the Hamilton County Democratic Party, said, "All of us hate dishonesty in our elected leaders. We cannot tolerate public corruption without tragic results to our society. Whether Billy Long’s resignation implies such a terrible indictment is yet to be seen. He will have his day in court.
"Today, the resignation of Sheriff Billy Long brings relief to all of us who felt Hamilton County had lost confidence in his leadership and character. His resignation also allows law enforcement to act effectively again. Finally, his resignation moves us forward so that we can now build new and strong leadership.
"Our hearts and prayers go out to the family and friends of Billy Long during the coming difficult days. And we will continue to support our law enforcement officers in all that they do."