The current captain of the Portugal national soccer team had been accused of raping Kathryn Mayorga in Las Vegas in 2009. He still faces a civil complaint from his accuser.
Cristiano Ronaldo will not face any criminal charges over an alleged rape in the US state of Nevada ten years ago.
The incident was alleged to have taken place in 2009 in a Las Vegas hotel room but Clark County District Attorney Steve Wolfson decided that Kathryn Mayorga's claim could not be proven beyond a reasonable doubt.
"Based upon a review of the information presented at this time, the allegations of sexual assault against Cristiano Ronaldo cannot be proven beyond a reasonable doubt. Therefore, no charges will be forthcoming," Wolfson said in a statement.
German magazine Der Spiegel and other partners in the European Investigative Collaborations (EIC) network last year revealed details from documents obtained via Football Leaks to expose wrongdoing in football, publishing Mayorga's renewed accusations of rape against the Juventus forward.
Mayorga underwent a medical exam in June 2009 to collect DNA evidence shortly after she claimed the incident took place. She spoke again with police for the new inquiry, and authorities this year obtained a sample of Ronaldo's DNA.
Police said the initial investigation was closed because Mayorga would not provide enough information regarding the identity of her attacker. She only said her attacker was a European soccer player and did not say where the rape occurred.
The investigation was reopened last year at the request of her lawyers.
Mayorga filed a separate civil lawsuit in a US federal court claiming Ronaldo used "fixers" to stop her pursuing criminal charges, including a payment of $375,000 (€334,000), which Ronaldo's lawyer has not denied. Her claim came in the wake of the #MeToo movement.
The 34-year-old Ronaldo has always refuted the allegations.
jsi/jm (AFP, AP, dpa)