Top seed Bruno Kuzuhara has capped a dream Australian Open debut on Saturday, adding the boys' singles trophy to his junior doubles silverware after a marathon tussle against Jakub Mensik.
MORE: Junior boys singles results AO 22
The Brazil-born American avenged a US Open defeat to the Czech fourth seed 7-6(4) 6-7(6) 7-5 in a battle which extended four hours and 43 minutes.
Having already triumphed alongside Coleman Wong on Friday, the 17-year-old became the fourth player from the US in the Open Era to claim the junior singles title, following in the footsteps of Andy Roddick, Donald Young and Sebastian Korda.
He was the first player since Czech Jiri Vesely in 2011 to sweep the singles and doubles events.
"It's an unfortunate way to win it but I'm wishing Jacob a speedy recovery. It was great fight," Kuzuhara said. "We pushed each other right until to the end. Great match...
"Every day the work we put in it's paying off as it's shown today. I'd like to thank everyone back home, all my friends, family who stayed up to watch this match. Everyone even back in Brazil… and to my friends in Japan."
Leading a set and at five-all in the second set, Kuzuhara survived a 15-minute battle on serve as he fended off three set point to force the second-set tiebreak, but after a 96-minute second-set slog, Mensik finally levelled on his fifth set point.
With neither teenager willing to give an inch in the deciding set, cramps began to take hold of the 16-year-old Mensik at 4-5, 40-0.
The 16-year-old showed enormous fight to level at 5-all at the three-hour, 29-minute mark and after winning a 33-shot rally serving to stay in the match at 5-6, the cramping worsened.
Back-to-back double faults were an unfortunate end to a mammoth battle as a wheelchair was required to carry off Mensik.
Kuzuhara paid tribute to the crowd, which included reigning Roland Garros champion Barbora Krejcikova, there to support her younger compatriot, Mensik.
"It's always an amazing tournament, one of the ones I've always wanted to come and play," Kuzuhara said. "I'd like to thank everyone in the stands. You guys were amazing tonight.
"The energy to the end, that's what pushed me through and that's why I'm here standing with the trophy."
Earlier, top seed Petra Marcinko secured her first junior Grand Slam triumph after she brought an end to Belgian Sofia Costoulas's run 7-5 6-1.
In a first-time showdown between the two 16-year-olds, Marcinko extended her winning streak since November to 14 matches.
MORE: Junior girls singles results AO 22
She became the first Croatian to win a junior major since Ana Konjuh and Borna Coric prevailed in the girls' and boys' singles at the 2013 US Open.
"The match has been really tough, like playing on Rod Laver (Arena) has been a great experience," Marcinko said. "I was, like, kind of nervous at the beginning because it was like big stadium, first time playing a Grand Slam final.
"I kept calm in important moments. I kept my game through all the time. I didn't, like, have big drops. Yeah, having this trophy, winning a Grand Slam, for me it's so big."
Eighth seed Costoulas, who was seeking to become the second Belgian junior champion at Melbourne Park after An-Sophie Mestach in 2011, recovered from 1-3 down in the opening set but surrendered a critical break at five-all.
Marcinko never looked back. With a set and an immediate break in hand her forehand inflicted increasing damage as she ran away with the second set to consolidate her place at the top of the junior rankings.
"(I saw) like a lot of pictures on the wall when we were eating. There was a lot of good players," Marcinko said. "All of them, I knew all of them. I was like, 'Oh, my God, imagine my name being there, my picture. That would be amazing'.
"I just want to see it. Next year I just want to see my picture there. I cannot wait for that."