Ten man Everton suffered their first Premier League defeat of the season as Southampton ran riot at St Mary's.
James Ward-Prowse and Che Adams' first-half goals saw the Saints move fifth while the Toffees remain top on goal difference.
Everton went into the game having taken 13 points from their first five games but missed injured captain Seamus Coleman.
Stuart Armstrong had a goal disallowed at 2-0 for offside.
Lucas Digne was sent-off with 20 minutes remaining for a stamp on Kyle Walker-Peters' ankle as the full-back raced away from the Toffees man in the second-half.
And the visitors never looked like scoring from that moment on.
Having lost their first two games of this season, Saints are now unbeaten in four and have three clean sheets in their past four matches.
Other Premier League Fixtures:
Wolves vs. Newcastle.
Arsenal vs. Leicester.