Juan Martin del Potro produced a truly sensational fightback to beat Marin Cilic in an epic encounter and set up a decisive fifth rubber in the Davis Cup final.
Having moved 2-1 up in the tie with victory in Saturday's doubles, Croatia looked set to earn their second Davis Cup title when world number six Cilic took the first two sets at Arena Zagreb.
However, Del Potro - who has been involved in a host of absorbing contests on his return to full fitness in 2016 - refused to give up and delighted the raucous contingent of visiting Argentinian fans by recovering to prevail 6-7 (4-7) 2-6 7-5 6-4 6-3.
Del Potro's magnificent victory, which took four hours and 53 minutes, means the winner of the competition will be decided by the final singles match between Ivo Karlovic and Federico Delbonis.
Argentina are seeking a first title, having been runners-up on four occasions, while Croatia's only previous success came in 2005.
Del Potro was almost in tears as he reflected on his victory, stating: "It's tough for me to say something, but I did my best, playing with these colours. It's amazing."
With the prime minister and president of his country watching on, Cilic raced into a 3-0 lead in the opening set, before eventually moving ahead in a tie-break.
The second set proved one-sided as Del Potro struggled to deal with his opponent's serve and powerful forehand, but a dramatic twist in the tale followed.
After pulling off one of the shots of the year in the form of a remarkable 'tweener' lob, Del Potro broke at 6-5 up to take the third set and again came good when it mattered as Cilic served to stay in the fourth.
Cilic did his best to respond amid an increasingly frenzied atmosphere, but there was to be no stopping Del Potro as he surged to a first career win from two sets down.