Mignolet, who has been at Liverpool for six years, is set to sign a new five-year contract with Club Brugge.
The shot-stopper still has two years left on his contract at Anfield, however, he has been playing second-fiddle to Alisson since the Brazilian's arrival at Liverpool last year.
Jurgen Klopp has indicated he would rather keep Mignolet for the season ahead, however with just four days to go in the transfer market, the boss will now be on the lookout for a new goalkeeper.
According to Dutch publication Het Nieuwsblad, Liverpool "only wanted to cooperate on a transfer under certain financial conditions," however "an offer from a top club did not arrive," giving Club Brugge the chance for his signature.
The Belgian outfit confirmed the move in a series of tweets on Sunday evening. It is believed that Liverpool will receive a fee of around £7m for the move.
Local Reds journalist Paul Joyce also confirmed the imminent transfer, adding that the Reds will be looking to sign a new No. 2.
Liverpool currently have goalkeepers Caoimhin Kelleher, Andy Lonergan, Daniel Atherton and Vitezlav Jaros on their books - however it is unlikely that Klopp will go into the new season with any of the quartet.
Mignolet has made 204 appearances for Liverpool since joining back in 2013 after making a £9 million move from Sunderland under previous manager Brendan Rodgers.