Constable Christopher Kelly, 28, smashed a tumbler into Michael Ijomanta's face, leaving him with horrific injuries and blind in one eye.
Trouble erupted in April last year at the Crutherland House Hotel, East Kilbride, South Lanarkshire, where both men had been attending a wedding.
Kelly, of Cambuslang, had been an evening guest at the reception, where 180 people were attending.
However, Mr Ijomanta, 29, who had travelled from Wellingborough, Northamptonshire, to be at his cousin's wedding, was left screaming in agony at the end of the night.
Kelly admitted assaulting Mr Ijomanta to his severe injury, disfigurement and impairment at an earlier hearing.
And yesterday the constable was jailed at Hamilton Sheriff Court and told he had avoided a five-year term only due to his early plea.
Prosecutor Natalie Henderson had told how Mr Ijomanta had been on the dance floor when an argument broke out. She said: "There was a lot of pushing and shoving and the accused felt himself being pushed.
"The accused had a glass tumbler in his hand and, as a result, he turned and threw the tumbler in the direction he thought he had been pushed from.
"The glass went directly into the face of the complainer, who was standing three feet away."
Mr Ijomanta was left with glass in his eye, and cuts to his forehead, cheek and nose.
A surgeon at Hairmyres Hospital, East Kilbride, later described the injuries as some of the worst he had ever seen.
Shelagh McCall, QC, defending, said: "It was not premeditated and he lashed out in temper without thinking it through.
"He says the consequences of it to the complainer have left him devastated.
"He would like to apologise to Mr Ijomanta but this may be of cold comfort.
"He is a kind man who was an active church-goer from a good family but knows he has lost the career he cherished and will be going to prison."
Sheriff Shiona Waldron said: "This was a shocking incident and has caused life impairment for the victim.
"I know from the Crown that the glass was thrown from three feet on a crowded dance floor with over 180 people on it.
"The surgeon who dealt with the injuries said they were similar to those of having a glass smashed into a face and he was left with injuries to his cheek and face.
"I have heard you have previously been of good character from character witnesses, which makes this incident all the more reprehensible and there is no alternative to custody."
Kelly, who had nearly four years police service, had been allowed to continue working despite the charges against him.
But he quit his post before sentencing.
A Police Scotland spokeswoman said: "Christopher Kelly is no longer a serving officer."
Mr Ijomanta was unavailable for comment.