The Italian struck in the 90th minute of the game to deny Burnley a result that would have ended a run of 10 league games without a win for Sean Dyche's men.
After Leicester City were held to a 1-1 draw by Stoke City earlier in the day, Burnley went into the game knowing a win would move them three points clear of Claude Puel's Foxes but they struggled to break down a resurgent Southampton side for over an hour.
Mauricio Pellegrino's Saints arrived at Turf Moor having lost just one of their previous five Premier League games and they looked determined to eke out a result, but the lack of a cutting edge in the final third looked set to let them down, as it has done so many times this season.
Burnley struck first in the 67th minute when Aaron Lennon, who provided the home side with a threat down both wings throughout the afternoon, whipped the ball into the box, where Ashley Barnes applied the final touch to take it over the line with his head.
But Gabbiadini latched onto Guido Carrillo's pass in the Burnley area and applied a clinical finish to leave the home crowd disappointed at the final whistle.
Burnley's former England winger Lennon showed good technique as he volleyed the first shot of the game from the edge of the Southampton box into the arms of goalkeeper Alex McCarthy.
The visitors responded with a sweeping attacking move, Nathan Redmond darting to the edge of the Burnley penalty area before threading a pass to Dusan Tadic, whose shot with the outside of his left foot was blocked by the legs of Clarets defender Ben Mee.
Burnley should have taken the lead when Matthew Lowton's marauding run reached the by-line and he crossed to Barnes, who cut the ball back to Lennon, but the diminutive playmaker saw his shot blocked after 28 minutes.
After a spell of Southampton pressure early in the second half, James Ward-Prowse tried a raking, low corner to the edge of the penalty area, where Redmond arrived to meet it but his shot failed to penetrate a crowd of Burnley defenders.
Jeff Hendrick raced clear of the Southampton defence just before the hour mark but McCarthy made himself big and pulled off a brave block at the Republic of Ireland international's feet before the loose ball was sent over the crossbar by Ashley Westwood.
The momentum was with Dyche's men and Barnes should have made it count when Westwood's looping cross picked him out in the box but his header lacked power and accuracy, trickling wide of to the right of the goal.
He was given another chance moments later when Lennon's cross was met by the boot of Johann Berg Gudmundsson and, after McCarthy's parry found the head of Hendrick, Barnes bundled the ball over the line from point blank range.
PIC: Ashley Barnes scrambles the Clarets ahead. Can they hold on? pic.twitter.com/lxLKXM6fXc— Burnley FC (@BurnleyOfficial) February 24, 2018
Burnley's claims for a penalty were waved away when McCarthy appeared to handle the ball outside the area moments later and the let-off allowed Southampton to chase an equaliser in the closing stages.
Substitute Josh Sims carved out space for himself 20 yards from goal and his curling right-footed shot looked destined for the top right corner of the net before Nick Pope palmed it onto the post.
But there was still time for more and Sims' cross found Carrillo, whose pass across the Burnley area was pounced upon by Gabbiadini and he took a touch before slamming the ball home from eight yards to ensure the points were shared.
Key Opta stats:
- Burnley are winless in their last 11 Premier League games (D6 L5), their longest such run in the competition since January 2010 (12 games).
- Southampton have not lost any of the last nine Premier League games in which they have started the day in the relegation zone (W4 D5), since a 1-0 defeat to Liverpool in December 2012.
- Saints have won just once in their last 15 Premier League matches (D8 L6).
- Manolo Gabbiadini netted his first Premier League goal in 15 appearances and first since bagging a brace against Newcastle in October 2017.
- Ashley Barnes netted his fourth Premier League goal of the season, no Burnley player has scored more this term (level with Chris Wood).
- The Clarets have failed to keep a clean sheet in each of their last five home PL games, this after keeping four shutouts in the five games before this run.