Saints, who have not been beaten by Wolves in 28 years, looked to be heading to a damaging defeat after two goals from Sylvan Ebanks-Blake either side of a Gregory Vignal equaliser from the spot.
Vignal was then dismissed for an 81st minute bust-up with Ebanks-Blake, but Southampton were rewarded for their never-say-die attitude in the fourth minute of stoppage time.
The unmarked Euell rose above the Wolves defence to head home a corner from Mario Licka to earn new Saints boss Nigel Pearson a third successive draw.
But it left Wolves fuming as they saw a third successive win snatched away from them in the most dramatic of circumstances to hit their hopes of forcing their way into the play-offs
Ebanks-Blake had belatedly sparked the game into life with his 61st minute opener when he latched on to a through ball from Stephen Elliot before powering into the area and beating substitute goalkeeper Michael Poke at his near post.
But Wolves' advantage proved to be short lived as Vignal coolly converted from the spot 13 minutes later. Referee Colin Webster had no hesitation in pointing to the spot when David McGoldrick was sent sprawling by Kevin Foley.
Vignal comfortably fired his penalty past Wayne Hennessey, but after experiencing the highs of that goal he tasted the lows when he was dismissed after a touchline clash with Ebanks-Blake.
Wolves needed just seven minutes to take advantage of their extra manpower and looked to have won the game when Ebanks-Blake pounced from close range after Andy Keogh had headed down a cross from George Elokobi.
But Wolves then went to sleep when Licka lifted over his cross and Euell sent the small band of visiting fans into raptures.