Wellington Silva has been cleared to play for Arsenal - four years after signing for the club.
The 22-year-old Brazilian, who was 18 when he joined the Premier League side in January 2011, has never been granted a work permit to play in England.
He has had five loan spells with different Spanish clubs and is currently at Almeria.
But the striker has tweeted a picture of his new Spanish passport, which will allow him to represent the Gunners.
"The good thing is slow in coming, but arrives with the greatest satisfaction in the world," he tweeted.
Silva arrived from Brazilian side Fluminense for a reported £3.5m fee. The former Brazil Under-21 forward will now be able to figure in Arsene Wenger's pre-season plans, after acquiring nationality of a European Union nation.
All non-EU players require a work permit to play in England, but must have featured in at least 75% of their home nation's competitive internationals in the two years preceding the application.
A club can appeal against a rejected application, based on the player's skill and experience - as Chelsea did successfully when signing Brazilian midfielder Willian from Anzhi Makhachkala in 2013.
In the event of an appeal, an FA panel decides whether the player's ability is of a high enough calibre and whether they can contribute significantly to the development of the English game.