Alfred Smith, aged 39, knifed Mervyn Davies at The Crown and Sceptre pub in Minsterley, near Shrewsbury, leaving Mr Davies's neck with a 10cm gash that was pouring with blood.
Shrewsbury Crown Court heard that Smith and Mr Davies had "known each other all their lives", and that Smith had become angry over a woman.
He went to the pub after work on December 10, 2021 carrying a Stanley knife. Witnesses shouted "He's got a knife", and Smith was heard saying: "I'll ****ing kill you!"
Smith stabbed Mr Davies on the back of his neck. Mr Davies was rushed to hospital where he was taken straight through A&E due to how heavily he was bleeding.
He received stitches and has been left with a scar. The court heard Mr Davies has had to have multiple follow-up appointments due to infections and now struggles to sleep.
Kevin Jones, prosecuting, said that Mr Davies's wife is now anxious about her husband going out and the scar has made Mr Davies conscious about his appearance.
Smith, of Oak Meadow, Bishop's Castle, pleaded guilty to one count of wounding with intent and one count of possession of a bladed article in a public place. He has two previous convictions for three offences, including affray.
Debra White, defending, said Smith was "genuinely remorseful for his actions", and that alcohol had been a factor.
Judge Peter Barrie jailed Smith for four-and-a-half years. He said it was "very difficult to understand" quite why Smith lashed out as he did and that it could have been "fatal".
"It is clear you were highly intoxicated," he said. "That may be an explanation, but it is certainly not an excuse for it."
On the injury to Mr Davies's neck which Smith caused, the judge added: "It left a scar which has been troublesome," and said it has caused "nasty issues" for Mr Davies.
Smith is expected to serve half the prison term in custody and the remainder out on licence.
Speaking after the sentencing, West Mercia Police Detective Constable Pete Emery said: “We’re pleased with the sentence handed to Smith today. We will not tolerate knife crime in our area, I hope this sentence sends a very clear message that we can and do take positive action against those responsible.
“The victim suffered a very serious injury which could have had far worse consequences.
“Carrying a knife is never acceptable. We will continue to do all we can to tackle street violence involving knives, and work diligently to identify those who are carrying knives as well as those involved in violent crime.”