Wembley bore witness to a superb encounter as expectant United faced a Saints side looking to win just the second major trophy in their history, the first having come 41 years ago when the sides met in the FA Cup final.
Manolo Gabbiadini’s brace had Southampton dreaming as Ibrahimovic and Jesse Lingard strikes were cancelled out, only for Ibrahimovic, pictured, to head home three minutes from time to clinch a hard-fought win.
Mourinho became the first United manager to win a major trophy in his debut season, and the Portuguese enjoyed a fourth League Cup triumph – a joint record with Brian Clough and Sir Alex Ferguson.
Few would have known United were the side making a record-equalling 49th trip to Wembley as Saints flew out the blocks and they should have been ahead in the 11th minute.when Gabbiadini turned home hard-working Cedric’s cross from the right. Inexplicably, assistant referee Stuart Burt raised his flag for offside, despite the Italian being clearly on and Ryan Bertrand not interfering with play.
Saints soon had further reason to feel aggrieved by the decision. Oriol Romeu was booked for a lunge on Ander Herrera, giving Ibrahimovic a chance from 30 yards and the in-form veteran took it with aplomb, firing home a stunning free-kick and wheeling off towards his fans in celebration.
Saints’ wall and goalkeeper Fraser Forster will feel they should have done better with the 19th-minute strike, which Claude Puel’s men busily went about cancelling out.
James Ward-Prowse and Dusan Tadic forced the returning David de Gea into action from the edge of the box in quick succession.
United were not attacking with the same regularity, but unlike Saints made their threat count.
Marcos Rojo was allowed through to lay off to Lingard just inside the box, and Southampton’s lack of pressure gave the attacking midfielder time to calmly side-foot past Forster.
But it was not a fatal strike, as Saints collected themselves. In first-time stoppage time, Ward-Prowse’s fine right-wing cross was met by a smart Gabbiadini touch, turning the ball past De Gea.
Southampton started the second half brightly, Nathan Redmond seeing an exquisite volley kept out by De Gea.
There was no let-up from Puel’s men. Steven Davis beat Anthony Martial to a header and Gabbiadini swivelled expertly, firing through a crowd into the bottom corner.
After Romeu had powered a header off a post,Lingard wasted a glorious 76th-minute chance, and then Marcus Rashford came close to scoring by forcing Forster into a near-post stop.
It was a frantic conclusion and Ibrahimovic secured the win. Unmarked from six yards, he powered home Herrera’s cross to secure a memorable win and send United fans wild.