Southampton's trip to the final has been marred by controversy since the beginning of the play-offs after the Saints were accused of spying on one of Boro's training sessions.
The official investigation is still ongoing - read all about 'Spygate' here.
The match itself began at a frantic pace as Middlesbrough struck early through Riley McGree, who swept home a low pass from Callum Brittain after a driving run down the right flank.
Southampton responded strongly, with Ryan Manning and Ross Stewart both going close, the latter missing a clear chance before controversy arrived when Stewart was pulled back in the box by Brittain, only for penalty appeals to be waved away.
The pressure eventually told in first-half stoppage time, as Manning’s volley from a Leo Scienza free-kick was parried by Sol Brynn and Stewart nodded in the rebound to level the score.
The second half saw Southampton dominate possession but struggle to create clear openings, with Brynn again denying them before Manning sent a rebound narrowly wide after a deflection off Luke Ayling.
As the game wore on, both sides looked increasingly fatigued in a contest that stretched deep into extra time.
In the additional period, Samuel Edozie was denied by a strong Brynn save as penalties loomed, but Southampton finally broke through when Shea Charles’ speculative cross-shot from distance evaded everyone and nestled into the far corner to seal the win.
Hull reached the play-off final after a 2-0 victory away at Millwall on Monday evening, following a 0-0 draw in the first leg of their semi-final.
Mohamed Belloumi and Joe Gelhardt were on hand to propel the Tigers to an unlikely date at Wembley following a wild campaign that started with a transfer embargo, just months after they scraped to survival on the last day of the 2024/25 Championship season.
The Championship final will take place on Saturday, 23rd May, with the winner joining Coventry and Ipswich in the Premier League.
Flashscore Man of the Match: Ryan Manning (Southampton)