Jeremy Sarmiento's 97th-minute winner completed a remarkable comeback as Ipswich returned to the top of the Championship with a dramatic 3-2 win over 10-player Southampton.
After Leicester's win at home to Norwich earlier on Easter Monday, Kieran McKenna's side knew only a win against Saints - who also retained ambitions of automatic promotion - would return them to the summit.
Leif Davis' brilliant early strike handed Ipswich the lead - but 10 minutes later, they were behind, thanks to sweeping Southampton moves that were finished by Che Adams and Adam Armstrong.
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Southampton dominated the ball for much of the game and looked to be heading towards a crucial victory until Nathan Broadhead's smart finish levelled the scores.
That goal changed the game, with Ipswich pushing for a late winner in front of a raucous Portman Road crowd.
James Bree's straight red card for bringing down Davis as he charged towards goal pushed Saints closer to the brink and Sarmiento completed the turnaround with a stabbed finish in the final minute of added time - sparking wild celebrations and a return to the summit with just six games remaining.
How Ipswich struck late again to move top
Perhaps the remarkable late scenes were inevitable. After all, the only team to score more goals after the 75th minute than Southampton in the Championship this season are Ipswich.
But McKenna’s side are just as capable of scoring early goals, too, and did so when Davis took down Sam Morsy’s clipped ball just inside the area before rifling a powerful shot inside Gavin Bazunu’s near post.
However, Ipswich fans had barely retaken their seats when their team were sliced open by a slick Southampton move, with Adams turning in the loose ball from Joe Aribo’s touch after being played onside by Davis.
The left-back was caught out again less than 10 minutes later, with Stuart Armstrong leaving several defenders in his wake before sliding the ball through to Adam Armstrong, who raced behind Davis and fired past Vaclav Hladky.
Southampton’s impressive first-half display suggested an instant return to the Premier League very much remained a possibility, while Ipswich’s task was made even harder when they lost Kieffer Moore to injury.
But Russell Martin’s side failed to score the third goal that may have ended Ipswich’s hopes, with Luke Woolfenden and Hladky making important blocks from Ryan Fraser and Adam Armstrong.
Ipswich may have been struggling to gain a foothold in the game but they knew just one moment could change their fortunes - and that came when Ali Al-Hamadi struck the post from the edge of the box.
That near miss roused Portman Road and moments later, Broadhead swivelled and found the bottom corner to level the scores, while Bree’s dismissal only increased Ipswich’s hopes of another late winner.
Sarmiento obliged when his shot trickled agonisingly beyond Bazunu, moving Ipswich four points above third-placed Leeds, while Saints are 12 points behind second-placed Leeds, albeit with two games in hand.
McKenna: We never took a backwards step
Ipswich's Kieran McKenna:
"It's an incredible effort against a really good team. I'm so proud of how the boys went about it.
"We played them in a brave manner and tried to go toe-to-toe. We never took a backwards step and the players got full reward.
"[The sending off] enhanced our chances. It makes you even more positive. We had our chances and (we scored) a really well-worked last goal."
Martin unsure over Wilcox future
Southampton's Russell Martin on Manchester United's approach for director of football Jason Wilcox:
"I would say give me at least 10 minutes to get over the disappointment of tonight and we'll chat at some point this week.
"I'm sure I'll have more for you. I've not spoken to the club.
"You know my feelings on Jason and I'll have a chat with him after. I've just had a text saying how proud he was of the performance.
"Once I'm told, I'll let you know."
What's next?
Ipswich's next game is away to rivals Norwich in the Championship on Saturday, live on Sky Sports; kick-off 12.30pm.
The Tractor Boys then host Watford on Wednesday April 10; kick-off 7.45pm.
Southampton are next in action on Saturday when they travel to Blackburn in the Championship; kick-off 3pm.
Saints then host play-off hopefuls Coventry on Tuesday April 9; kick-off 7.45pm.