A brilliant goal from Danny Ings gave Southampton a narrow but deserved win over Jose Mourinho's Tottenham.
The Saints striker flicked the ball superbly over Toby Alderweireld before shooting past Paulo Gazzaniga for his ninth goal in his past 10 games.
Spurs were unimpressive, with Jan Vertonghen missing their best chance from close range in the first half.
Mourinho, who was booked late on, sees his team stay sixth in the table, while Southampton rise to 11th.
Spurs striker Harry Kane was forced off with a leg injury just seconds after having a goal disallowed for offside in the second half.
Southampton claimed a penalty against Alderweireld for handball early in the second half, but the referee did not give it and VAR upheld the decision, then also upheld the official's decision against Kane when he netted later on.
Mourinho was shown a yellow card by referee Mike Dean after appearing to go over to speak to members of the Southampton coaching team.
A 2-2 draw with Arsenal on 23 November left Southampton one place off the foot of the table on just nine points, but since then Ralph Hasenhuttl's side have hit a run of form to move away from the relegation zone.
The win over Spurs means they have collected 16 out of a possible 24 points since that meeting with Arsenal, and they worked tirelessly to both give themselves chances and to frustrate the visitors.
Southampton 1-0 Tottenham Hotspur: Hasenhuttl praises 'confident' Ings' 'fantastic goal' And Ings' goal brought back memories of Paul Gascoigne's famous strike against Scotland in Euro 96, with the striker touching a long pass from Jack Stephens over Alderweireld before allowing the ball to bounce up invitingly for the 27-year-old to score his 13th league goal of the season.
Southampton's energy levels dipped in the second half, but they held on to restrict Spurs to just one shot on target after the break.
It was their fourth clean sheet of a campaign that has veered away from the depths of the 9-0 humiliation at St Mary's by Leicester on 25 October towards signs that Southampton can stay in the Premier League with some comfort.
As brilliant as Ings' goal was, it underlined a defensive frailty that continues to hang around Spurs despite an upturn in results under Mourinho.
The 5-0 win over Burnley on 7 December is the only clean sheet they have kept in 11 games since Mourinho's appointment.
Southampton 1-0 Tottenham Hotspur: Mourinho denies defensive problems in 'strange game' But in addition to their problems at the back, Spurs appeared disjointed going forward and they will be looking forward to the return of Son Heung-min from his three-match suspension to give them some impetus in attack.
The sight of Kane limping off the field, clutching the back of his thigh seconds after seeing his goal disallowed, was another bad moment for Spurs but it was compounded by their manager soon after.
And the manager got in on the action too. Mourinho strode out of his technical zone to say something to a member of the home side's coaching staff, and was immediately shown the yellow card to cap an unhappy day on the south coast.
The ex-Liverpool and Burnley striker's goal will linger long in the memory, and if he keeps up the form that has brought him 13 goals in 21 league appearances, Southampton have a great chance of staying up Manager reaction
Southampton manager Ralph Hasenhuttl speaking to Match of the Day: "I must praise the team for this unbelievable character, mentality and passion. The whole stadium was flowing today. When it is like this, it makes it really fun to play in."
On Danny Ings' goal: "It was fantastic. Such a goal you make when you have lots of self-confidence. This time of the season is unbelievable."
On keeping a clean sheet: "It is a fantastic job. This is only possible if you defend with the discipline that we did today. Until the last line we were very committed. Everybody was brave and on the front foot. Even when we won the ball we tried to play football. If you are brave then you deserve to get something and today we got a lot. It was important for us that we start winning at home especially against a strong side. It was not undeserved."