Saints played well for a large chunk of this game, but were undone in the end and suffered their first Premier League home defeat to Arsenal since 2003/04.
Alexis Sanchez opened the scoring on the hour mark, turning inside the box and hitting home.
The Gunners were comfortable after that and doubled their lead on 83 minutes as Sanchez found Aaron Ramsey at the back post, who nodded it on to Giroud to head in from close range.
Saints now winless in five games – their worst run of the season.
On top of that, their home struggles continue and Claude Puel looks more and more under pressure.
Photographer Stuart Martin was at St Mary's Stadium - check out the pictures above
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