Transfer guru Fabrizio Romano says the potential transfer is all-but done.
Taking to social media, Romano tweeted: "Arsenal have reached full agreement with Sao Paulo to sign Brazilian winger Marquinhos, born in 2003.
"Done deal, set to be signed - contract until June 2027.
"Fee will be around €3.5m (£3m) guaranteed.
"And Arsenal are also preparing their opening bid for Gabriel Jesus."
Marquinhos, who has been capped three times for Brazil's Under-17s. has chipped in with three goals and one assist from 15 games in all competitions this season.
The North London outfit have managed to secure a cut-price fee for the 19-year-old following a legal issue.
Marquinhos was thought to be tied down to a five-year deal at Sao Paulo - a contract he signed in 2019.
However, Fifa have now ruled that the contract is only valid for three years - the maximum length for a player signing their first professional deal.
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