All over. A huge win for Southampton. They have won in the league for the first time since November and are out of the relegation zone.
Follow reaction here.
Ben Foster launches one into the Southampton penalty area but it's headed away. Southampton win the ball back and there are only seconds left.
Here come West Brom. One last attack?
Mario Lemina has been excellent today. He breaks up a West Brom attack, carries the ball away from danger and then wins a free-kick near halfway.
Lemina stays down and a few more seconds will be wasted. Matt Phillips gets booked for the foul.
FIVE minutes added on. A massive five minutes in the Premier League relegation battle. Southampton are up to 14th as it stands from 18th at kick off. The Baggies are four points adrift at the bottom as it stands.
Big sighs of relief for the Baggies. Ahmed Hegazi barges Shane Long over in the penalty area but the flag was already up for offside.
A final Southampton change. Nathan Redmond comes on for Dusan Tadic.
Another sub. Sofiane Boufal is being replaced by Pierre-Emile Højbjerg. Boufal takes his time in getting off the field.
What a chance.
If Southampton don't end their 12-game winless run today I'm not sure Shane Long will sleep too well. He is unmarked at the back post after being picked out with a lovely cross from the right but heads over the bar.
Unsurprisingly the home fans cheer sarcastically.
Big appeals from Jay Rodriguez for a West Brom penalty. He's just inside the penalty area as he takes a long ball on his chest and is barged over from behind by Ryan Bertrand. The home fans also want a spot-kick but the referee shakes his head.
Chris Brunt leads the Baggies protests.
The Regis family are watching on from a box in the stands at the Hawthorns. I'm sure they're desperate to see the Baggies snatch an equaliser or better.
Alan Pardew is going for this. Left-back Allan Nyom off. Winger James McClean on.
First change for Southampton. A lively full debut for Guido Carrillo comes to an end as he is replaced by Shane Long.
Long is booed by the home fans as he enters the battle against his old club.
Game back on! Chris Brunt gets his second brilliant assist of the day with a great swinging cross from the left. It is so inviting that you can see the goal coming before the ball even reaches Salomon Rondon in the middle and the Venezuelan just climbs to nod the ball in at the back post.
What a game this is.
This could be a talking point. The lively Oliver Burke nips in in front of Jack Stephens on the edge of the penalty area. Burke gets the ball in front of Stephens but the sliding Southampton centre-back seems to catch his ankle. Burke stays on his feet but can't get to the ball after his heavy first touch. Had he gone down that may well have been a penalty.
James Ward-Prowse to take the free-kick again but he fires over. Just.
Craig Dawson has just kept West Brom in this. The Baggies defence is cut open in a flash and Dusan Tadic looks certain to square to debutant Guido Carrillo for the striker to tap in but McAuley slides in with a crucial interception. Southampton are back in their passing groove. West Brom have spent the last two minutes chasing shadows and now Boufal wins another free-kick in a dangerous position.
Straight away it is clear West Brom have something different with the rapid Oliver Burke on the pitch. He beats Cedric in a sprint but the Saints full-back fights back well to regain possession. West Brom are just starting to be encouraged by a few sloppy Southampton passes.
West Brom are four points adrift at the bottom as it stands and Alan Pardew is making two attacking changes.
Daniel Sturridge full debuts comes to an end as he is replaced by Jay Rodriguez and Oliver Burke comes on for defensive midfielder Claudio Yacob.
Southampton are really starting to grow in confidence now. Mario Lemina tries a clever flick to get in behind but the touch is a little too strong.
At the other end Salomon Rondon slices way, way wide. The Baggies are going to introduce Jay Rodriguez in a moment.
Southampton have breathing space. James Ward-Prose curls the ball low to the bottom right corner and, despite the shot coming to his side, Ben Foster can't get down to stop it.
There was a bit of a tussle before that goal between Sofiane Boufal and Ward-Prowse with Boufal wanting to take the free-kick but he's the Moroccan is the first man to celebrate with Ward-Prowse following the goal!
Another free-kick opportunity, this time for Southampton.
Wesley Hoedt goes on a surging run and is tripped just outside the box.
This is a really end to end second half. Dusan Tadic goes close and then West Brom look dangerous on the counter-attack but choose the wrong pass.
The Saints then take the opportunity to calm things down and Mario Lemina gets his foot on the ball in midfield.
This is really, really silly from both Sofiane Boufal and Allan Nyom. The pair get in a tangle on the halfway and Boufal swings a leg in the direction of his opponent. Boufal doesn't really connect and Nyom belatedly falls to the ground in a heap. Neither player is booked. Sensible refereeing from Michael Oliver.
Moments later, Chris Brunt goes for a Kevin de Bruyne-eque free-kick - shooting under the wall as the opponents jump - but it is flicked wide.
Daniel Sturridge has had plenty of the ball so far but just doesn't quite look at his sharp best which is understandable really. He drifts with the ball on the right but then his chipped through ball dribbles harmlessly through to Alex McCarthy in the Southampton goal.
The tensions are starting to grow inside the Hawthorns. A few groans follow.
Back under way. Southampton are 14th as it stands. West Brom are five points from safety.
The day started so well with an early goal but two Southampton goals have pushed West Brom into a lonely-looking last place in the table.
Alan Pardew needs to find something, and fast.
It's been a really entertaining game so far and Southampton will feel they deserve the lead. They have dominated possession and Guido Carrillo has looked lively up front.
Chris Brunt bends one around the wall but Alex McCarthy gets down well to palm the ball away. It was the goalkeeper's side as they say but came through bodies and was well-hit. Good save.
West Broom have a free-kick around 19 yards out, just to the right of centre. Can they hit back straight away?
We're into added time.
What a turnaround. Two goals in a matter of minutes and now Southampton are in front. All credit to Jack Stephens. He was at fault for West Brom's opener and has made up for it with a brilliant, near-post header.
He runs to meet James Ward-Prowse's corner and flicks the ball up and just inside the back post.
It's the Southampton fans you can hear now. The Saints force another corner.
What. A. Hit.
Southampton have dominated possession and get their equaliser. Guido Carrillo forces a brilliant save from Ben Foster but the resulting corner is squared to Mario Lemina 20 yards out and the former Juventus midfielder arrows a rocket into the top-left corner. Unstoppable.
What was a saying about Daniel Sturridge? That's his first big chance.
The England striker spins his marker on the left side of the box and, following a nice through-ball, is in on goal. He takes his shot early on the bounce but it goes narrowly over the bar. A top-form Daniel Sturridge buries those.
Again Southampton surge forward and look dangerous. Cedric curls a cross in from deep on the left and Dusan Tadic just can't get a crucial touch at the near post. Alan Pardew has had a little word with Salomon Rondon, seemingly some tactical advice. Rondon and Daniel Sturridge have been quite after a lively opening 10 minutes.
Gareth McAuley has taken a bang to the head and that gives Maurico Pellegrino the chance to give out some orders of his own.
Guido Carrillo is not the biggest centre forward but he has played a couple of nice touches to hold the ball up.
Following another good bit of play from the Argentine, a mix-up at the back presents Dusan Tadic with a chance but his shot is blocked and it loops over onto the top of the net. The corner comes to nothing but the Saints are on top now.
Another big chance and it's another corner from Chris Brunt. The Northern Irishman whips another great delivery in from the right that goes between three or four players at the near post. The ball finds it's way all the way to the goal scorer Ahmed Hegazi at the back post but he is taken by surprise. It just hits the Egyptian and is cleared off the line.
Guido Carrillo is getting closer. He hasn't found the target yet but the £19m-striker is looking really bright. A good cross from the right comes in from Mario Lemina and Carrillo gets ahead of both of the Baggies centre-backs but flicks his header two yards wide of the post.
Southampton have responded well to going behind. Gareth Barry has just become the first player in the book today due to a late foul on Oriol Romeu. It was nasty and he can have no complaints.
It's wasted this time. Chris Brunt's corner is hit way too hard and the opportunity is lost.
West Brom are still showing good intent though. They snap at the heels of Mario Lemina in midfield and force a loose pass, resulting in a throw-in inside the Southampton half.
Can West Brom repeat the trick? Southampton have gifted them another corner after a mix up at the back...
First chance for Guido Carrillo.
After that corner was cleared, Southampton come again through Dusan Tadic and Argentine Carrillo. The pair play a one-two which releases Carrillo on the edge of the area but the Saints' record-signing scuffs his shot wide of the left-hand post.
Alan Pardew is out on the touchline with his arms folded giving instructions to his players. The Baggies have only won one of their 11 games under Pardew. Will today be the day they earn a second win under the Englishman?
They've got a bit of work to do. Southampton earn their first corner.