A jury decided the case against Peter Barrowman, 35, was not proven following a trial at the High Court in Glasgow.
Speaking outside court, the father-of-two from Stenhousemuir told BBC Scotland that the verdict was a "massive relief".
He said: "I am so happy that I can go home. I can't really put it into words, but I'm just very happy."
Mr Barrowman, who worked at Cornton Vale prison, is currently suspended by the Nursing and Midwifery Council.
Asked if he would seek a return to nursing, he replied: "That's a decision I've still to make."
Three women - all prisoners in the jail - claimed Mr Barrowman raped them between January and March 2014 while they were his patients.
He denied any sexual contact with the women and claimed they were lying.
The nurse was suspended from working at Cornton Vale in March 2014, after the allegations were made and he was dismissed in July last year.
Mr Barrowman was also acquitted of charges of supplying drugs to prisoners. The charges were withdrawn by the Crown before the end of the trial.
A former mental health nurse has been cleared of raping three women in the prison where he worked.