The visitors played some scintillating football at Portman Road and stretched their club-record run to nine successive victories.
Saints, under the guidance of Nigel Adkins, appear to be real promotion contenders based on early-season evidence and have certainly maintained the momentum of last term as they stormed to promotion from League One.
In Rickie Lambert and David Connolly they have two strikers who will bag goals aplenty in the second tier, aided by free-flowing support play from the likes of Adam Lallana and Guly Do Prado.
It was Lambert, a player Ipswich manager Paul Jewell admitted he tried to snare in the summer, who bagged an early brace to put the visitors firmly in command after just 11 minutes. Connolly added his third goal of the season just before the break.
Ipswich, in fairness, had first-half chances to reduce the arrears and, following an impacting double half-time substitution, had Saints on the ropes as Keith Andrews and Jay Emmanuel-Thomas made it 3-2 with half an hour remaining.
But Lallana added a classy fourth and a stoppage-time fifth for Southampton to ensure the south-coast outfit are the early pace-setters at the top of the Championship.
Confident Saints started the clash firmly on the front foot and Lallana had already dragged a decent chance wide when Lambert broke the deadlock.
The former Bristol Rovers marksman played a neat one-two with Connolly before sending the ball home from 12 yards.
The visitors were causing plenty of problems going forward and, with Town's defence at sixes and sevens, Lambert doubled his tally for the evening with a super curling strike into the bottom corner after more eye-catching build-up play, this time involving Lallana.
Guly sent an effort narrowly wide after 18 minutes as Saints threatened a third.
And the prospect of seeing the game move out of sight before the end of the first quarter sparked a Town revival.
Lee Bowyer latched onto a lofted throughball but saw his solid effort well saved by former Town stopper Kelvin Davis, before another good move presented Aaron Cresswell with a great chance to register his first goal for the club but he somehow sent his left-footed strike wide.
But, as Ipswich probed for a route back into the affair, Saints strengthened their grip with a third minutes before half-time.
Lallana broke and found Guly, the Brazilian rounded David Stockdale and found space to square the ball for Connolly to fire home from close range.
Jewell brought on Emmanuel-Thomas and Lee Martin at the break and the changes certainly had a positive effect.
It was Andrews, on loan from Blackburn, who grabbed a lifeline in the 56th minute, following up well after Michael Chopra's stunning strike had rebounded off the crossbar.
Cresswell made a crucial goal-line clearance from Lallana which would have swung the game back in Saints' favour.
And no sooner had the hosts made vital contributions at both ends as they made it 3-2 as Emmanuel-Thomas converted from close range.
But Lallana ended the comeback in the 76th minute when he latched onto Morgan Schneiderlin's through-ball to convert past Stockdale.
And there was still time for a late fifth as the midfielder used his pace to confirm a third home defeat in a week for the Tractor Boys.