The 21-year-old has penned a four-year deal with the Tigers, which includes a club option of a further year.
The popular Iranian international first moved to the MKM Stadium on loan from the Turkish giant in January.
He made 12 appearances for the Tigers – six of them starts – and scored his only goal in a 2-1 victory over Cardiff City which mathematically secured the Championship status.
Sayyadmanesh started his senior career with Esteghlal in his homeland before signing for Fenerbahce in May 2019.
Sayyadmanesh, who is Iran’s youngest-ever goalscorer, has also enjoyed loan spells with Turkish team Istanbulspor and Ukrainian outfit Zorya Luhansk.
His performances for the latter, where he scored 12 goals in 35 league matches, saw him named one of the Ukrainian Premier League’s best 11 players for 2020-21.