As we previously reported, Kathryn Mayorga claims Ronaldo raped her in a Las Vegas hotel room back in 2009.

She claims she met CR7 at Rain Nightclub in the Palms hotel in June 2009 and he invited her up to his penthouse suite to party and hot tub. There are photos of Mayorga and Ronaldo hanging out at the nightclub together that evening.

She had initially filed a police report describing the alleged crime -- but didn't identify Ronaldo by name.

Mayorga sued Ronaldo claiming she later accepted a $375,000 payment in exchange for her silence -- but recently announced she wants that agreement voided and went to cops to pursue a criminal case against Ronaldo.

In court documents, Mayorga described the alleged attack ... saying while changing her clothes in the penthouse suite, "Ronaldo entered the bathroom, exposed his erect penis and asked [her] to perform fellatio."

Mayorga claimed she refused and wanted to leave -- but Ronaldo "pulled [her] into a bedroom and onto a bed and attempted to engage in sexual intercourse."

Mayorga claims she tried to fight Ronaldo off -- but he turned her onto her side and sodomized her while she screamed "no, no, no."

Ronaldo had adamantly denied the allegations -- and said, "Rape is an abominable crime that goes against everything that I am and believe in."

Now, the Clark County District Attorney’s Office has made a decision to NOT prosecute -- claiming "the allegations of sexual assault against Cristiano Ronaldo cannot be proven beyond a reasonable doubt."

Prosecutors described the situation in detail ...

"On June 13, 2009, a female victim ('V') placed a call to the Las Vegas Metropolitan Police Department and reported that she had been the victim of sexual assault.  Members of law enforcement responded to her location to take a crime report.  Police transported V to the hospital so that a sexual assault examination could be conducted."

"A short time later, sexual assault detectives arrived at the hospital and made contact with V.  Although she knew who the person was who assaulted her, V refused to identify him or disclose where the crime occurred.  As a result, the police were unable to follow investigative protocols for sexual assault cases or to conduct any meaningful investigation.  Without knowing the identity of the perpetrator or the location of the crime, detectives were unable to search for and impound vital forensic evidence.  In addition, video evidence, showing interactions between the victim and perpetrator before and after the alleged crime, was lost.  The criminal investigation was closed."

"V and Cristiano Ronaldo, through their respective attorneys, eventually reached a civil settlement related to this matter in 2010.  For the next eight years, law enforcement heard nothing more from V regarding the crime or the perpetrator."

"On August 28, 2018, V contacted the Las Vegas Metropolitan Police Department, asking that her sexual assault investigation be reopened, naming Cristiano Ronaldo as the offender.  In spite of the passage of over nine years, Metro investigated her allegations."