Ireland and Ulster rugby players Paddy Jackson and Stuart Olding have been cleared of rape.
They both denied raping the same woman in Mr Jackson's house in the early hours of 28 June 2016.
Blane McIlroy, who was accused of exposure, and Rory Harrison, who was charged with perverting the course of justice and withholding information, were also found not guilty.
The verdicts came in the ninth week of the trial.
Mr Jackson was also cleared of a charge of sexual assault.
The jury of eight men and three women deliberated for three hours and 45 minutes before delivering their unanimous verdicts.
Before discharging the 11-person jury, Judge Patricia Smyth told them: "This has probably been the most difficult trial that any jury in Northern Ireland has ever been asked to adjudicate on."
The incident at the centre of the case was alleged to have happened after the four accused and four women went to Mr Jackson's home in south Belfast from a club in the city centre.
The woman told the court she was attacked after going upstairs to retrieve a clutch bag as she was preparing to leave the house.
The woman claimed Mr Jackson had followed her into the bedroom and pushed her onto the bed. She then claimed she was raped.
However, the accused said that all sexual activity was consensual.
Outside the courthouse, Mr Jackson thanked the judge and jury for "giving him a fair trial" as well as his family and legal team.
His solicitor, Joe McVeigh, hit out at the investigation into Mr Jackson.
"It's our belief that the investigation has been characterised by the turning of a blind eye to inadequacies in the evidence of the complainant combined with the very apparent investigative bias," he said.
He added: "The prosecution made much of a perceived privileged position provided by virtue of Paddy being an international rugby player.
"We say that it was this very status as a famous sportsman that drove the decision to prosecute in the first place."
Mr McVeigh also said "real concerns about the integrity of the trial process" had been raised by "vile commentary expressed on social media, going well beyond fair comment".
"Several days of this trial were lost due to problems thrown up by the intrusive infection of the process by social media," he said.
"All the lawyers have been distracted by having to man the barriers against a flood of misinformed, misconceived and malicious content on the internet, particularly during the last phase of this trial and, worryingly, even at the hands of public servants who should have known better."
At the court
by Mark Simpson, BBC News NI
There was no reaction from the four defendants in the dock as the verdicts were announced.
They simply stood and stared in front of them as, one by one, the not guilty verdicts were read out by the chairperson of the jury.
A number of their friends and family were in tears in the public gallery.
Outside Court 12, Paddy Jackson hugged members of his legal team, as well as friends and family.
Relatives of all the four accused attended every day of the 42-day trial.
The case was only scheduled to last five weeks. In the end, it went on for eight-and-a-half weeks.
In a statement read out by his solicitor, Mr Olding said: "I want to acknowledge publicly that though I committed no criminal offence on the evening of the 28th of June 2016, I regret deeply the events of that evening."
He said he was sorry for the hurt that was caused to the complainant.
"It was never my intention to cause any upset to anyone on that night," he said.
"I don't agree with her perception of events and I maintain that everything that happened that evening was consensual.
"I have consistently told the truth to the police and the court when asked to account for my conduct."
Blane McIlroy made no comment as he left with his parents and legal team.
The Public Prosecution Service (PPS) defended the decision to take the case to court.
In a statement, Marianne O'Kane, assistant director of the PPS's serious crime unit, said: "The evidence received in this case was subjected to a very thorough and careful examination by a team of experienced lawyers including senior counsel, before we concluded that the test for prosecution was met, in line with our code for prosecutors.
"This meant that there was both sufficient evidence to provide a reasonable prospect of conviction and it was in the public interest to prosecute.
"This case was properly brought before the courts and overcame a number of legal challenges. It was ultimately right that the matter was placed before a jury to make their determination."
The senior investigating officer in the case, Det Ch Insp Zoe McKee, said she had spoken to the complainant following the verdicts: "Understandably, she is upset and disappointed with the outcome."
She said the case was "thoroughly and robustly investigated. We pursued all lines of investigative inquiry, we brought all of the evidence together, we worked in close collaboration with the Public Prosecution Service from the start".
Her colleague, Det Ch Supt Paula Hillman added: "I am satisfied that this was a very thorough investigation carried out with professionalism and integrity."
In a joint statement, the Irish Rugby Football Union and Ulster Rugby said it had "undoubtedly been a difficult and extremely traumatic time for all involved".
They added that an internal review had been postponed pending the end of judicial proceedings and that a review committee has been appointed and "will conclude its review as soon as practicable".
"The players will continue to be relieved of all duties while the review committee is in process and determining its findings."
The verdicts came at the end of a 42-day trial.
The 12-person jury which started hearing the case was later reduced to 11 after a juror took ill.
In total, 30 witnesses gave evidence, including 10 police officers, the four defendants, the alleged victim and the taxi driver who drove her home on the night in question.
The court sat on weekdays, but, to try to make up lost time, there was one Saturday sitting.
Some hearings in the eight-and-a-half week trial were taken up with legal arguments, in the absence of the jury.
On the second week of the trial, the jury was taken to see the layout of Paddy Jackson's house.
All the other proceedings have taken place in Court 12 at Laganside courts complex. On most days, the 100-seat public gallery has been full.
Paddy Jackson, 26, from Oakleigh Park, Belfast, and his Ireland and Ulster teammate Stuart Olding, 25, of Ardenlee Street in the city, denied raping the same woman at a house in south Belfast in June 2016.
Mr Jackson denied a further charge of sexual assault.
Blane McIlroy, 26, of Royal Lodge Road, Belfast, denied exposure while Rory Harrison, 25, of Manse Road, denied perverting the course of justice and withholding information.