Fenerbahce will pay 19.5 million euros (£16.5 million) over four years for the 27-year-old Moroccan, who becomes the biggest transfer in the history of the Turkish Super Lig.
"Welcome to Fenerbahce Youssef En-Nesyri," wrote the Istanbul club on X, marking their first big signing since the arrival of their star Portuguese coach in early June.
En-Nesyri, who has scored 20 goals in his 73 internationals for Morocco, netted 73 goals in 196 appearances for Sevilla, with whom he won the Europa League in 2020 and 2023.
It was his header against Portugal that sent the Atlas Lions through to the semi-finals of the 2022 World Cup where they lost to France.
He will play up front in Istanbul alongside the veteran and prolific Bosnian Edin Dzeko.
Fenerbahce, who have not won the title since 2014, are aiming to end the longest title drought in their history next season.
Last term, they finished second in the Super Lig behind arch-rivals Galatasaray.
