Arsenal have signed Marquinhos from Sao Paulo on a long-term contract.
Marquinhos, 19, a Brazil youth international, made 33 appearances for Sao Paulo and won the Compeonato Paulista in 2021.
"We're delighted to have completed the transfer with Sao Paulo, as Marquinhos was a player we had been watching for a while," Arsenal technical director Edu said.
"At 19, he is still very young, so he is a player for the future. We look forward to Marquinhos now joining us for preseason, making his new home, and continuing to grow and develop with us."
ESPN reported last month that the deal would be worth €3.5 million and that the clubs agreed a fee after Marquinhos rejected multiple contract offers from the Brazilian club and sources suggest Arsenal moved quickly to secure a cut-price agreement.
Marquinhos is a left-footed forward also able to operate as a winger but he is viewed by Arsenal as a future prospect rather than an immediate first-team signing.