Jack Clarke struck a late equaliser for Ipswich to end Southampton's automatic-promotion dream in an enthralling 2-2 draw, which will take the race for the Premier League to the final day.
An explosive second half at St Mary's had seen Wes Burns put Ipswich ahead, before Ryan Manning and Cyle Larin turned the game on its head for the Saints.
Southampton knew they needed a victory to take their charge towards second into the final day, but Clarke's late goal knocked them out of the race.
Ipswich are now a point clear of Millwall and two clear of Middlesbrough heading into Saturday's lunchtime finale, with every game live on Sky.
Millwall are at home to already-relegated Oxford United while Middlesbrough head to Wrexham, who need a result themselves to book a place in the play-offs.
Saints will be in the play-offs and they face Preston on Saturday.
After a tense first half, the game exploded into life in the second.
After Jacob Greaves dispossessed Tom Fellows in midfield and lifted the ball over the top, Ivan Azon nodded across the box for Burns to lash beyond Daniel Peretz.
The advantage only lasted 10 minutes. Greaves was booked for a lunging challenge on Finn Azaz just outside the Town box and from the resulting free-kick, Manning’s low effort flicked off Marcelino Nunez to fly into the roof of the net via the leg of the wrong-footed Walton.
Southampton knew only victory would be good enough to keep them in contention for a top-two finish.
A moment of magic turned the match in the home side’s favour in the 80th minute.
Manning drove forward and slid a pass into Canada international Larin, who calmly stepped inside Greaves and Leif Davis to stab the ball beyond Walton.
A four-way final-day promotion shoot-out was on the cards but Clarke hauled Ipswich level three minutes from time by firing his 16th league goal of the season into the bottom right corner.
The winger twice came close to a late winner, striking a post and then forcing a last-gasp save out of Peretz while Darnell Furlong also headed narrowly wide as a breathless encounter ended all square.
Southampton boss Tonda Eckert speaking to Your Site:
"We started the second half very strongly. We conceded off a situation where we shouldn't have, but then it just shows where we are as a team that we can turn games back in our direction.
"We kept pushing and compliments to Ipswich today, it was two teams finishing on a high off the back of a very tough schedule.
"I would have loved to have won it today, but overall it was a very good game. You saw the dedication and we tried everything to win the game.
"It's crunch time now, but we have clarity and we need to get ready for the play-offs."
Ipswich boss Kieran McKenna speaking to Your Site:
"I thought it was an outstanding game. One of the best in my time, certainly in the Championship, I'll put it right up there. I thought it was a top game. I loved our performance.
"To do that at this stage of the season, here with the form they're in, I think is a great sign for where we're at as a group.
"You probably can't come much closer to getting promoted than we were at the end, in terms of a matter of inches from the ball going in the net.
"But I loved where we're at, and we look forward to Saturday night."
Kevin Phillips on Your Site Football:
"Kieran McKenna will have taken that before the game. It was so difficult to prepare for for Ipswich.
"Southampton knew they had to win. It was such an entertaining match.
"Each side had good spells, and I think a draw overall was a fair result.
"As a neutral, we wanted it to go to the last day of the season. Roll on Saturday, it's going to be some day."
