A judge has directed that a jury find Martin Earley not guilty of the murder of Sandra Collins in Co Mayo in 2000.
Mr Earley, of Carrowmore-Lacken in Mayo, walked free from the Central Criminal Court in Castlebar today.
The decision to acquit the 50-year-old came on the fifth week of a trial where he had been charged with the murder of Ms Collins.
She was last seen in the village of Killala in Mayo in December 2000.
The prosecution finished presenting its case yesterday.
The defence then made an application that there was not enough evidence to warrant the case proceeding further.
In a lengthy judgment delivered today, Mr Justice Patrick McCarthy said that while he was of the view that Ms Collins had died on the night of 4 December 2000, in his view, there was insufficient evidence to prove beyond reasonable doubt that the crime of murder had been committed.
During the trial, evidence had been heard that Mr Earley had been in a relationship with Ms Collins for a number of weeks prior to her disappearance.
The case brought against Mr Earley had been entirely circumstantial.
The jury had been told her body had never been found and there was no specific crime scene identified.
Relatives of Ms Collins family broke down in court today.
Mr Earley was also in tears after the jury was directed to find him not guilty.
The Collins family issued a statement after today's decision saying that they are "naturally, very disappointed at the current developments."
However, the family said they "recognise and appreciate the judge's decision" and "acknowledge the legal rights of the accused."
They said they will never give up the search until they find Sandra.