Portsmouth climbed out of the Sky Bet Championship relegation zone after Ebou Adams marked his home debut with a 77th-minute equaliser to earn a 1-1 draw with fierce rivals Southampton.
Saints were on course for a first league win at Fratton Park in 50 years following Leo Scienza's 57th-minute opener.
But the visitors were denied south-coast derby bragging rights when Pompey midfielder Adams - a January signing from Derby - headed in following an Adrian Segecic corner, to spark wild celebrations.
Portsmouth leapfrog Blackburn into 21st place courtesy of the point, while Southampton remain 15th after their wait for a clean sheet on the road stretched to 25 league games.
Saints made the short journey along the M27 having not won a league match on Portsmouth's patch since 1976, albeit this was just the fifth such meeting during that period and first for 15 years.
Rival managers John Mousinho and Tonda Eckert exchanged words on the touchline during a frantic start to the contest in which the visitors had a golden chance to snatch an early lead.
Following a delightful flick from Kuryu Matsuki in midfield, Saints' 11-goal top scorer Adam Armstrong was sent through on goal by Finn Azaz, only for his low effort to repelled by the left foot of Nicolas Schmid.
Pompey goalkeeper Schmid then produced another smart stop to again deny Armstrong, diving to his right to keep out a thumping half-volley after James Bree crossed from the right.
Portsmouth enjoyed plenty of first-half possession but created few clear chances.
Forward Millenic Alli side-footed narrowly wide for the hosts before a deflected effort from Segecic dipped on to the roof of the net.
Southampton boss Eckert had called for "cold heads and hot hearts" from his players amid the hostile atmosphere.
His side silenced three sides of the ground 12 minutes into the second half when Scienza, who claimed Saints' winner in the 1-0 midweek success over Sheffield United, broke the deadlock.
With Portsmouth appealing in vain for offside, the Brazilian winger raced clear on to Azaz's pass before calmly beating Schmid and then taunting home supporters as he ran the length of the pitch to celebrate with the 2,651 travelling fans.
Tempers threatened to boil over with 20 minutes to go after Flynn Downes' tackle on Zak Swanson as the home team attempted to break from a corner sparked a melee and resulted in a booking for both players.
Pompey had struggled from an attacking perspective for much of the afternoon but levelled 13 minutes from time.
Segecic's inswinging corner from the right caused chaos in Southampton's six-yard box and Adams endeared himself to Portsmouth's fans by bundling home his first goal for the club in front of the stunned away end.
Mousinho's men ended a feisty affair in the ascendancy but could not find a winner during six minutes of added time as, for the second time this season, the derby ended in a draw.
Portsmouth's John Mousinho:
"It was an amazing occasion. It felt very different to the game back in September (a 0-0 draw at St Mary's).
"I thought it was a proper derby: the intensity, the aggression, the way it was played. There were a couple of flare-ups and a couple of big tackles which maybe on another day in a different occasion probably result in red cards.
"I thought it was a really brilliant occasion to be a part of. The only disappointment is we didn't win because I thought we could have done at the end.
"But if I look at the overall chances created and the way the game went I think it was a fair result.
"As a spectacle, it was brilliant. It was a proper old school derby, not a tactical battle. It was a really good game."
Southampton's Tonda Eckert:
"I think that the chances were quite clearly on our side, especially in the first half.
"And then when we do go up in the second half, we just need to make sure that we bring the game over the line. I think we deserved more.
"The 15 minutes after the first goal, we were clearly on top and you need to use those moments to score a second goal, and if you don't you need to make sure you see a game out.
"It's a good corner, a scramble in the middle, and we need to just deal better with those situations.
"It's a non-negotiable that we have to leave everything on the pitch and we did this to a hundred per cent."
