Saints conceded only 36 seconds into the game, as James Maddison opened the scoring, and by the end of a dizzying first 25 minutes they were 4-0 down, with further goals following from Son Heung-Min, Dejan Kulusevski and Pape Sarr.
Any hopes of avoiding further misery by half time were dashed with another strike from Maddison only moments before the whistle to make it five, with the scoreline at least not worsening from there in the second half.
Russell Martin made four changes from the team that lost 1-0 at Aston Villa last weekend, as Alex McCarthy returned from injury to replace Joe Lumley in goal, while Jan Bednarek was also fit to feature for the first time since the visit to Wolves in early November.
Jan Bednarek made his return from injury against Spurs (Photo: Matt Watson)
He came in for Nathan Wood, who joined Lumley among the subs, while the other alterations saw Kamaldeen handed a first start of the season, with Joe Aribo also restored to the line-up, as James Bree and Cameron Archer switched to the bench.
Also named as a substitute was Paul Onuachu, who was back in the matchday squad for the first time since the 3-2 loss to Liverpool in late November after recovering from injury.
Facing a Spurs team that had won just one of their past eight, and none of their previous five, there was hope that Saints could earn their second Premier League win of the season.
But they made the worst possible start, conceding the opening goal within 36 seconds.
Maddison was the scorer, finishing low past Alex McCarthy, but much of the credit belonged to Djed Spence, who had driven forward from halfway before sliding a perfectly-weighted through pass in behind the defence for his teammate’s run.
The trouble then deepened for Saints on 12 minutes, as Spurs doubled their advantage.
Maddison turned provider this time, with his cross from the right flicking off the head of Bednarek and falling to Son at the back post, and the Tottenham captain made no mistake, striking a crisp, low, left-footed shot past McCarthy.
Less than two minutes later, Spurs added a third.
Son’s low cross from the left went towards Dominic Solanke, who was well challenged by Bednarek six yards out, but the ball then spun into the path of an unmarked Kulusevski, who side-footed home from close range.
Martin immediately made a change, bringing on Wood for Kamaldeen, as he switched to a back five.
Nathan Wood was introduced after only 15 minutes, following three early Spurs goal (Photo: Matt Watson)
Saints did then have an opportunity to pull one back, as Tyler Dibling’s delivery from the right found the run of Adam Armstrong in behind, but his header went straight at Fraser Forster in the Tottenham goal.
On 25 minutes, it became 4-0.
Son was the provider this time, with his square pass from the left finding Sarr on the edge of the box, and he took a touch forward, shifting the ball onto his left foot before finishing into the corner of the net.
It would have been five on 34 minutes but for McCarthy making a fine save to tip over a rising shot from Son on the counter attack, as Spurs showed no signs of relenting.
Saints did go close themselves soon after, as Dibling fed the ball to Ryan Manning in space on the left, but his low, first-time cross was turned just wide of the near post by Armstrong.
McCarthy was then called into action twice in the closing stages of the half to make further saves from Son and prevent the scoreline worsening.
But there was nothing he could do to stop it happening with the last kick of the half, as Son’s pass into the area found Maddison, who cut back from the byline and somehow finished across goal, just inside the angle of post and crossbar, to make it 5-0.
Saints endured a gruelling first half against Spurs (Photo: Matt Watson)
Saints at least saw the back of Son at the interval, after he was withdrawn having tormented the hosts with a goal and two assists. His absence took some of the edge off the threat posed by Spurs and made the start of the second half far less painful than that of the first.
Martin then made a change of his own around the hour mark, as Yuki Sugawara was introduced for Manning, and his counterpart at full-back, Kyle Walker-Peters, almost got Saints on the scoresheet soon after, driving into the left side of the area before firing a low shot narrowly wide of the near post.
On 70 minutes, they had another chance to find the net, as Aribo’s clipped delivery found Wood in space, but he side-footed wide of the far post as the ball dropped to him.
Even when they did get the ball in the net, on 79 minutes, it was ruled out for offside, with Mateus Fernandes having started his run a little too early before heading home from a Flynn Downes cross.
The game then petered out from there, as Saints were left to reflect on a chastening evening, with attention now turning to Wednesday night's Carabao Cup quarter-final at home to Liverpool.
Southampton: McCarthy, Walker-Peters, Harwood-Bellis, Bednarek, Manning (Sugawara 62), Downes, Aribo, Fernandes, Dibling, Kamaldeen (Wood 15), Armstrong (captain) (Archer 82).
Unused substitutes: Lumley, Bree, Fraser, Amo-Ameyaw, Lallana, Onuachu.
Booked: Fernandes.
Tottenham: Forster, Spence (Dorrington 77), Gray, Dragusin, Udogie (Pedro Porro 28), Sarr, Bergvall, Maddison (Werner 77), Kulusevski, Solanke (Lankshear 82), Son (captain) (Johnson 45).
Unused substitutes: Austin, King, Hardy, Olusesi.
Goals: Maddison (1’, 45+4’), Son (12’), Kulusevski (14’), Sarr (25’).
Booked: Bergvall, Maddison, Johnson.
Referee: Darren England.