The deal is worth a guaranteed £60 million and includes a sell-on clause, bringing an end to the Brazil international's time in north London. Martinelli has signed a four-year contract with Al-Hilal, who are currently joint-top of the Saudi Pro League alongside Cristiano Ronaldo's Al-Nassr.
The 25-year-old joined Arsenal from Brazilian club Ituano in 2019 and quickly became an important part of the team. However, with just 12 months remaining on his Arsenal contract, Martinelli was informed by manager Mikel Arteta that he was no longer central to his plans for the new season.
"Proud to be blue, proud to be Al-Hilal," Martinelli said in a video posted on the Saudi club's social media channels following his unveiling.
Martinelli will join an increasingly high-profile squad at Al-Hilal, with England striker Ollie Watkins also arriving at the club this summer from Aston Villa in a £51 million transfer.
The Saudi side have further strengthened their attack with the signing of Dutch winger Crysencio Summerville from West Ham. The club is managed by former Inter Milan boss Simone Inzaghi, who took charge after Al-Hilal's summer recruitment drive.
Martinelli is also expected to receive a significant increase in salary. Reports suggest his wages at Al-Hilal will be considerably higher than the approximately £180,000 per week he was earning at Arsenal.
The winger made 53 appearances across all competitions for Arsenal last season, scoring 11 goals as the club secured the Premier League title for the first time since 2004.
Despite that contribution, Martinelli was not included in Arsenal's first two matchday squads of the new campaign. Arteta had indicated that the Brazilian would face limited opportunities if he remained at the Emirates Stadium.
The decision to leave Martinelli out of the squad also drew criticism from former Arsenal striker Ian Wright.
"The way Martinelli is being treated at the moment, it really makes me feel uncomfortable," Wright told Sky Sports.
Wright acknowledged that Arsenal may have wanted to move the player on, but argued that the club should have handled the situation in a way that also considered Martinelli's interests and how he wanted to leave.
Martinelli now begins a new chapter in Saudi Arabia as Al-Hilal continues to build a squad capable of competing for domestic and international honours.
