Olivier Giroud scored a hat-trick, as the Gunners ended the season in second place, one point ahead of their North London rivals, Tottenham Hotspur.
Spurs, who were in a two-horse race for the title as at April, were hammered 5-1 at St James Park by a relegated Newcastle team.
Manchester City also clinched the last Champions League ticket, despite being held to a 1-1 draw by Swansea. The result means that no matter what happens in a rescheduled match between Manchester United and Bournemouth, it is City who will play in the bigger European competition.
Leicester were held to a 1-1 draw at Stamford Bridge, Everton defeated Norwich 3-0, Southampton crushed Crystal Palace 4-1 and West Brom held Liverpool to a 1-1 draw at the Hawthorns