The Brazilian forward signed a long-term contract with the Premier League club.
Martinelli netted 10 goals in 34 games after making his debut in 2017.
Speaking about the move, Martinelli said:
I model my game on Cristiano Ronaldo,
He is a player who works hard, pushing himself to the next level. Always in the run for titles and individual trophies.
This is a dream since I was a child and also my family’s dream for me to be playing in Europe and playing for a big team like Arsenal. I am going to take this opportunity.