Leo Ostigard has completed a permanent move to Serie A side Napoli for undisclosed terms, subject to international clearance.
The Norwegian international impressed in Italy during the second half of last season while on loan with Genoa, prompting the interest from Napoli.
Technical director David Weir said, "Leo's had really successful loan spells in Germany, Italy and here in the UK in the Championship with Coventry City and Stoke City, so it was no surprise he attracted such interest from a top Italian club like Napoli.
"He is also keen to play regular senior football and establish himself as a permanent player. That was not something we were able to guarantee for Leo, so the transfer is good for both clubs and the player.
"It's testament to the club's academy, development programme and loan system, and equally to Leo. He has worked very hard and been an absolute professional in his approach and attitude.
"This transfer is a direct result of that dedication and professionalism on the training pitch, day to day and in matches. On behalf of the club I would like to wish him well in his future career and for the season ahead."
Leo will have the prospect of Champions League football with Napoli this season, after the club finished third in Serie A behind AC Milan and Inter.
Leo joined Albion from Norwegian Eliteserien side Molde FK in August 2018. He spent the 2019/20 season on loan with German second division team St Pauli and, following an impressive spell there, with a season at Championship outfit Coventry.
He received his first international call up to the Norwegian senior squad in September 2020, and has made five appearances for his country.
Last season he spent the first half of the season on loan with Stoke before a move to Genoa in the January window.