Arsenal announced a new deal worth £60m-a-year from 2019 on Monday, ending and doubling their current £30m contract with Puma.
It is their first deal with Adidas since 1994.
The contract brings Arsenal into line with some of the biggest earners in the Premier League - the matches the yearly income for Chelsea in their deal with Nike, according to the Daily Mail.
Chelsea signed a bumper 15-year contract with Nike in the summer of 2017, just after becoming Premier League champions under Antonio Conte.
United's contract with the German manufacturer is the largest in the top flight, worth £75m a year.
City, despite having won the Premier League by a record margin last summer, have the smallest yearly income from their kit deal of any of the established top six, at £20m a year with Nike.