The 25-year-old forward joins Arsenal having established himself as one of the leading strikers in the Premier League in recent seasons. He scored 95 goals in 236 appearances in all competitions during his five seasons in Manchester.
Technical Director Edu said: “We are delighted that we have secured the transfer of Gabriel. Everyone who knows football well, knows the qualities of Gabriel Jesus.
"Gabriel is a player who we have admired for a long time now. He is 25 years old and an established Brazil international who has consistently demonstrated that he is a player at a very high level.
"We look forward to seeing him join up with his new teammates ahead of the new season. We all welcome Gabriel to Arsenal."