Ronald Koeman's side struck three times in the opening half and, although their attacking play was impressive, they were helped on their way to a club-record top-flight win by a number of mistakes from the visitors.
Santiago Vergini's spectacular own goal after 12 minutes gave Southampton the lead, with Graziano Pelle, boosted by a goal on his Italy debut on Monday, capping a memorable week with his fifth league goal of the season six minutes later.
Jack Cork added the third before half-time, substitute Liam Bridcutt bundled home a second own goal just past the hour and Pelle made it five with his second after 68 minutes.
Dusan Tadic, Victor Wanyama and Sadio Mane completed the rout in the closing minutes as Southampton, who are unbeaten at home this season, stay third in the table.
Meanwhile, Sunderland remain in the bottom half after suffering their heaviest defeat of the campaign.
The hosts began in positive fashion and were gifted the opener as Vergini fired into his own net.
Shane Long, recalled for Mane as one of two changes, played a neat one-two with Pelle, but as Vergini tried to get the ball under control he volleyed beyond Vito Mannone from the edge of the box.
Sunderland, who recalled Wes Brown for Billy Jones, continued to be their own worst enemy as a mistake from Will Buckley led to Southampton's second goal six minutes later.
The midfielder's attempted clearance struck the back of Sebastian Larsson, the loose ball was rolled onto Steven Davis and his low cross was tapped home by the in-form Pelle.
Fraser Forster had maintained a watching brief up to that point but he was called into action after 20 minutes, the England international getting down well to parry Larsson's free-kick.
With half-time looming Steven Fletcher saw a penalty shout waved away, and to rub salt into Sunderland's wounds Koeman's side added a third eight minutes before the interval.
Tadic superbly found Cork at the back post and his effort somehow beat Mannone, who should have done better.
Pelle was causing the Sunderland defence all kinds of problems and, after setting up Davis for a chance on goal, he saw his effort cleared off the line by Patrick van Aanholt.
The fourth goal eventually came three minutes after the hour, though.
Ryan Bertrand raced clear on the left, his pull-back found Pelle whose effort saved, but Bridcutt clumsily turned the ball into his own goal from two yards.
As Sunderland began to sink without a trace Pelle added a fifth, the striker latching onto a Tadic pass before firing across Mannone.
To add to Sunderland's nightmare they conceded another two goals inside as many minutes as first Tadic and then substitute Wanyama got themselves on the scoresheet.
Tadic capitalised on a dreadful clearance from Mannone to fire into an empty net from 25 yards, and a minute later Wanyama lashed home the seventh from inside the penalty area.
If Sunderland thought the scoring was over they were wrong, as substitute Mane made it eight with four minutes to play with a simple finish from another Tadic delivery.
