London - Barcelona signed promising Arsenal teenager Marcus McGuane on Tuesday on an initial three-year contract that includes a 22.5 million ($31 million, 25 million euros) release clause.
McGuane caught the eye of Barcelona with his performances for Arsenal's Under-23 team.
The midfielder has moved to the Spanish club for an undisclosed fee and will initially join up with the Barcelona B squad.
Barcelona B compete in Spain's second-tier Segunda division, which is the equivalent of the English Championship.
Barca have an option to extend the 18-year-old's contract by a further two years.
London-born McGuane graduated from Arsenal's youth academy after joining the Premier League club at under-six level.
"We would like to thank Marcus for his contribution and wish him well at Barcelona," an Arsenal statement read.
England Under-19 midfielder McGuane played twice for Arsenal's first team this season in Europa League ties against Red Star Belgrade and BATE Borisov.
Speaking about McGuane last year, Arsenal manager Arsene Wenger said: "He is a defensive midfielder, and overall he can play as a wing-back or even a centre-back in training."
A Barcelona statement added: "McGuane's deal will keep him at Barca for three seasons, plus two option years. The buy-out clause has been set at €25m."