Willian believes Mikel Arteta can turn Arsenal back into Premier League title contenders.
The Brazil international revealed manager Arteta as the main reason he has joined the Gunners, after ending his seven-year stay at London rivals Chelsea.
Arsenal completed Willian's signing on Friday on a three-year deal worth a reported Stg220,000 ($A400,000) a week.
The 32-year-old attacking midfielder admitted former Manchester City assistant Arteta had sold him a bold vision for the Gunners' future.
"I decided to join the club because Arsenal is one of the biggest clubs in the world, and because of the new project with Arteta," Willian, who will wear the No.12 shirt at Arsenal, said.
"I think this club deserves to shine again, and I want to be a part of this project.
"With Arteta, I think Arsenal have a great opportunity to fight again for titles in the Premier League and in Europe.
"I am excited to start, I can't wait to get on the pitch to do my thing to help my team-mates and the club to shine again.
"I talked to (Arteta) and the conversations were good. He gave me confidence to come to Arsenal, he said a lot of good things to me, and that's why I have come to Arsenal."
Willian helped Chelsea to two Premier League titles, one FA Cup triumph and the 2019 Europa League, when the Blues thumped Arsenal 4-1 in the final Baku.
But the 70-cap Brazil star was forced to watch from the stands as Arsenal edged out Chelsea 2-1 in this year's FA Cup final, having been sidelined with an ankle problem.
Blues boss Frank Lampard had been clear all season that he wanted to keep Willian at Stamford Bridge, with the club offering him a two-year extension.
The Blues were unwilling to meet his demands for a three-year deal, however, and now he has switched London allegiances.
Arsenal boss Mikel Arteta admitted he was impressed by Willian's desire to join the north London club.
"I believe he's a player that can really make a difference for us," said Arteta.
"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.
"He is a player that gives us a lot of versatility, he can play in three or four different positions."