The angry woman persuaded staff at nightspot Noah's Yard in Swansea's Uplands district to put up the sign reading ‘Paul...I am divorcing you’ above the door.
Her statement was then followed up with a further message proclaiming: ‘BTW I am keeping the dog’.
The wife, who wished to remain anonymous, went into Noah’s Yard — which has a history of changing the words on its sign — on Tuesday to ask for the sign to be put up at the weekend.
She said the reason behind her doing it was to name and shame her husband after finding out he allegedly had an affair.
'I was angry and upset so wanted a sign to go up for everyone to see,' she told the South Wales Evening Post.
'When I found out I went through a mixture of emotions but felt angry and wanted him to pay.
'I am absolutely devastated and going through a really tough time at the moment.
The wife said she had messaged Paul to tell him to go read the sign and he was furious when he saw it.
Linda Davies, who lives close to the bar, said: 'Good on her. If my husband ever cheated on me then I would string him up by his privates.
Passerby Ron Williams said it would keep a lot of men in the area on their toes.
Noah’s Yard changes the words on its sign on a regular basis, often displaying statements such as 'Go Wales' for rugby matches.
The bar once had a romantic proposal emblazoned above the entrance, coincidentally reading 'Marry Me Paul', although it was no known if the same woman was behind the sign.
It also supported the city of culture campaign by emblazoning the campaign logo on its premises.
Noah Redfern, owner of Noah’s Yard, said they have had a lot of unusual messages displayed on their building before — but this was definitely a first.