Ocmulgee Circuit District Attorney Fred Bright said the 20-year-old student's accusations could not be proven beyond a reasonable doubt, and her lawyer said in a letter that she did not want to press charges.
"Therefore there will be no arrests made nor criminal prosecution against Mr. Roethlisberger," Bright said.
The woman told an officer Roethlisberger sexually assaulted her early March 5 at the Capital City night club, where he was drinking with friends shortly after his 28th birthday.
Bright said the investigation showed the woman was heavily intoxicated that night. She and her sorority sisters had met Roethlisberger at a different bar earlier in the night, and he invited them into a VIP area at the Capital City club and ordered them shots. When the woman walked down a hallway to a small bathroom, Roethlisberger followed her.
What happened in that bathroom is unclear, Bright said. A doctor who examined the woman could not say if she was raped, and while some DNA was found, there was not enough to determine whom it belonged to.
"We are not condoning Mr. Roethlisberger's actions that night," Bright said. "But we do not prosecute morals. We prosecute crimes."
He said local and state investigators spent weeks questioning witnesses even though the woman sent a letter urging prosecutors not to move forward with charges.
"I know when I have a case and I know when I don't," Bright said. "And I do not have enough evidence to convince 12 jurors beyond a reasonable doubt that Mr. Roethlisberger was guilty of rape."
Bright said the woman told him it had been an "unnerving experience" and that she and her family made it clear they did not want the matter prosecuted.
One of the 20-year-old woman's attorneys, David Walbert, said in a letter to Bright that his client was not recanting her accusation. But the letter, released to the media Monday, said she did not want to go to trial because it would be "a very intrusive personal experience."
Lee Parks, another attorney for the woman, said in a statement that he was pleased Bright honored his client's request.
J. Tom Morgan, a former DeKalb County district attorney, said Georgia laws set a high bar for proving sexual assault and require proof that force was used.
"If this is sexual assault, it has to be proven that it happened without consent, and that's difficult especially if both parties consumed alcohol," said Morgan, who is now a sole practitioner.
Roethlisberger was seen out with a few friends at several different bars that night. The Capital City club is a popular spot for students at the neighboring Georgia College & State University. Roethlisberger owns a home about 30 miles north on Lake Oconee, in central Georgia.
The two-time Super Bowl champ is being sued by a different woman who says he raped her in 2008 at a Lake Tahoe hotel and casino, an allegation he denies. Roethlisberger has not been criminally charged in that case either and has claimed counter-damages in the lawsuit.
Roethlisberger has not taken part in recent offseason workouts with the Steelers.
As Pittsburgh's first-round draft pick out of Miami of Ohio in 2004, Roethlisberger led the Steelers to Super Bowl victories in 2006 and 2009. He frequently has donated time and money to charities, and his charitable foundation awards a police dog to a department near every Steelers road opponent.
But off-field problems have come along with his championships and $102 million contract. In 2006, he defied his coach's orders and rode his motorcycle without a helmet and wound up with a concussion, broken jaw and other injuries after a wreck.
And while Roethlisberger has a reputation for patiently signing autographs and posing for pictures while out in public, he also is known for occasionally inelegant behavior in Pittsburgh.
Early in his career, he was photographed obviously after drinking wearing a T-shirt reading "Drink Like a Champion."
Bright said "quite candidly… there was too much drinking going on" at the bar during the night in question - both by people over and under 21.