The Toffees announced the news on Twitter:
The deal was officially announced after the Premier League's summer transfer deadline had already passed. Iwobi signed a five-year deal.
The 23-year-old Nigeria international is a product of the Arsenal academy, making his first-team debut in 2015. He made 22 Premier League starts last season, scoring three goals and adding six assists.
Sky Sports' Matt Cheetham is a fan:
While the winger can struggle with his finishing―he has never scored more than three goals in a Premier League season―he is an expert at setting up team-mates:
The Toffees already signed a young ace striker in Moise Kean earlier this season, so finding a solid creator to provide him with service was their next objective.
Iwobi's development slowed in the last few seasons, but he often struggled to get a consistent run in the team at the Emirates Stadium and should benefit from the more regular playing time he's likely to receive at Goodison Park.
Arsenal will miss his ability to create, but after signing Nicolas Pepe from Lille, they were always likely to cash in on one of their wingers. The Ivorian is a far more productive option out wide, scoring an impressive 22 goals in Ligue 1 last season.