Paddy Jackson and team-mate Stuart Olding had always denied raping the same woman at a house in south Belfast in June 2016.
Jackson was also found not guilty of sexual assault, a charge he also denied.
The jury of eight men and three women at Belfast Crown Court returned its unanimous verdict after deliberating for a total of three hours and 45 minutes.
The foreman answered “yes” when asked by a court clerk if the 11-member panel had reached a verdict on which they were all agreed.
Both 26-year-old Jackson from Belfast, and 24-year old Olding, also from Belfast, are now free to resume their sporting careers which lawyers said were “blighted” by the false rape claims.
The pair had always denied raping the now 21-year-old woman, who cannot be named for legal reasons, during a party in Jackson’s home on June 28, 2016.
They maintained from the outset that any sexual contact they had with her in Jackson’s bedroom was purely consensual.
Acquitted and freed along with them were two friends, Blane McIlroy (26), from Belfast, cleared of exposure, and Rory Harrison (25) also from Belfast, who had denied charges of perverting the course of public justice, and withholding information.
In a joint statement following the verdict, the IRFU and Ulster Rugby said: “The IRFU and Ulster Rugby note the verdict handed down today at the Belfast Crown Court in relation to the case brought against Paddy Jackson and Stuart Olding. We wish to acknowledge that this has undoubtedly been a difficult and extremely traumatic time for all involved.
“To respect the judicial proceedings the IRFU and Ulster Rugby postponed any internal review of the matter with the players, until the proceedings concluded.
“IRFU and Ulster Rugby officials will review the matter, in line with existing procedures for all contracted players. A Review Committee, made up of senior representatives of the IRFU and Ulster Rugby, 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.”
This story was first featured on our sister site The Belfast Newsletter.