Born in Düsseldorf, the centre back began his senior career at Schalke 04, making his Bundesliga debut as a teenager against Hoffenheim in March 2020.

He went on to play 61 times for Die Königsblauen, scoring three times, before making the move to San Siro in August 2022. In his first year in Italy, he played alongside future Magpies teammate Sandro Tonali, and made his Champions League bow for Milan.

The following season, Thiaw lined up against Eddie Howe's side in the same competition as United returned to European football's top table with a goalless draw at San Siro, with the defender helping the hosts record a clean sheet. In all he made 85 appearances for Milan, netting once against Real Madrid, and currently has three Germany caps to his name.

Thiaw will wear the number 12 shirt for the Magpies, and joins fellow summer recruits Anthony Elanga and Aaron Ramsdale in Howe's squad.