Moreira joined Benfica from Standard Liege in 2020 and was part of the side that won the 2022 UEFA Youth League.

Having made his senior debut in May 2022, Moreira featured regularly for Benfica B last season.

The teenage winger is part of Portugal’s squad at the European Under-21 championship, where it will face England in the quarter-finals on Monday (AEST).

Moreira’s arrival on a free transfer follows on from the signings of forwards Nicolas Jackson from Villarreal and Christopher Nkunku from RB Leipzig, while Ruben Loftus-Cheek has completed a permanent move to AC Milan.

Loftus-Cheek’s departure is one of several recent outgoings as new Blues boss Mauricio Pochettino reshapes his squad ahead of the start of the season.

Arsenal completed the signing of midfielder Kai Havertz, while N’Golo Kante, Kalidou Koulibaly and goalkeeper Edouard Mendy all headed for Saudi Arabia.

Midfielder Mason Mount is also set to depart after Manchester United agreed to sign the England international for an initial fee of £55 million ($108 million).