Willian will wear the number 12 shirt at Arsenal after completing a transfer from Chelsea.
The Brazilian has put pen to paper on a three-year deal with the Gunners, believed to be worth around £100,000-a-week.
Mikel Arteta revealed his delight at getting the transfer for the 32-year-old over the line.
“I believe he’s a player that can really make a difference for us,” said the Arsenal boss.
“We have been monitoring him for the past few months, we had a clear intention to strengthen in the attacking midfielder and the winger positions [and] he is a player that gives us a lot of versatility.
“He can play in three or four different positions.
“He has the experience of everything in the football world but to still have the ambition to come here and contribute to bring the club where it belongs.
“I have been really impressed with all the talks I have had with him and how much he wanted to come.”
Willian will link up with David Luiz at Arsenal.
Technical directer Edu added: “I know him very well, since a long time ago because we’ve been working together for the Brazilian national team and of course I was following him because he played for another club.
“He has a lot of fantastic attributes as a person, as a football player of course, his character.
“I’m 100 per cent sure that everybody in the dressing room, the fans, myself and Mikel will enjoy having Willian in our side.”
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