Ronald Koeman's Saints put behind them a five-game winless run to hammer the Gunners who could have gone top of the table had they amassed three points on the south coast.
Cuco Martina opened the scoring with a remarkable swerving strike from distance in the 19th minute which gave Petr Cech no chance before Shane Long added a second 10 minutes into the second half when slotting home Sadio Mane's pinpoint cross.
Southampton grabbed a third when Jose Fonte powerfully nodded home Ryan Bertrand's corner prior to Long rounding out the triumph when racing onto Dusan Tadic's through ball and fired between the legs of Cech.
- What a performance from the Saints. Can this be the catalyst for a big second half of the season?
- Once again, just when everything seems to be going well for Arsenal, they produce a shoddy showing like this. What can Wenger do to instil some solidity?
Happy with my goal, but even more happy with the win! #wemarchon@SouthamptonFCpic.twitter.com/duz4iNXEeg
— Cuco Martina (@CucoMartina) December 26, 2015
We really needed this performance and victory! What a great night! #BoxingDay photocredit: Pro Shots/Action Images pic.twitter.com/SEaHGh38AT
— Jordy Clasie (@JordyClasie) December 26, 2015
"We will be ready to bounce back." - @PetrCech reflects on the defeat to Southampton: https://t.co/4UYgSyGOAPpic.twitter.com/KB7IybR3ti
— Arsenal FC (@Arsenal) December 27, 2015
Southampton boss Koeman rated his side's win as 'perfect':
"Of course, we don't expect this result. We had confidence, we had belief to win the game, but so clearly in the end to win 4-0, and even to have good opportunities to score more goals.
"Well, I think Southampton made the game very physical.
"We lost too many challenges and that explains why we lost the game. But that's one aspect, so well done to them."