Jannik Sinner fought back from a set down to claim his fourth title of the season with victory over Alexander Zverev in the Vienna Open final.

The top seed, who is currently on a 21-match-winning streak on indoor hard courts, battled through early hamstring cramps to seal the 3-6 6-3 7-5 win in just under two and a half hours.

It marks Sinner's second title of the month, having won the China Open at the start of October, while he also added to his Grand Slam haul with victories at the Australian Open and Wimbledon earlier in the year.

"It feels amazing," Sinner said after lifting his 22nd Tour-level title. "It was such a difficult start for me. I tried to stick in there mentally, trying to play my best tennis when it counts.

"It has been such a special week. It is always the highlight of my calendar to come and play here in Vienna."

Sunday's final was the pair's first meeting since Sinner beat Zverev in straight sets in the Melbourne final back in January.

Zverev, the 2021 Vienna Open champion, looked to have a strong foothold in the final, though, after gaining a double-break advantage at 4-1 in the first set.

From there, the German only needed to hold serve to seal the first set 6-3 in 46 minutes.

But Sinner dug deep and looked revived in the second set, playing a number of well-placed winners to hold serve twice and break serve, opening up a 3-0 advantage.

The rest of the second set was relatively straightforward for the world number two, but he and Zverev went toe-to-toe in the deciding set, before Sinner broke serve at 5-5.

From there, he opened up three Championship points before Zverev netted a simple backhand into the net.

"I would like to congratulate Jannik Sinner, whose level has been off the charts for these last two years," said world number three Zverev.

"For me, he is currently the best player in the world. This week, he was simply the best player in Vienna."

Earlier, Great Britain's Julian Cash and Lloyd Glasspool secured their seventh Tour-level title of the season with a 6-1 7-6 (8-6) win over Austria's Lucas Miedler and Portugal's Francisco Cabral.

The Britons needed just 70 minutes to claim their first title since winning the Canadian Open on 7 August.

Fonseca claims maiden ATP 500 title

Joao Fonseca has become the third-youngest ATP 500 champion since the series began in 1990 with a straight-set victory over Alejandro Davidovich Fokina at the Swiss Indoors.

The 19-year-old continued his rapid rise up the rankings by scooping up the biggest title of his career with a 6-3, 6-4 win over the Spaniard, who holds a 0-5 record in Tour-level finals.

Fonseca also became the first Brazilian to win a title above the ATP 250-level since Gustavo Kuerten claimed the ATP Masters 1000 title in Cincinnati in August 2001.

"It is crazy", Fonseca said. "My parents just got here from Brazil. They were going to Paris but changed their flights and came here one hour before the match.

"It is just amazing to have them here for the biggest title of my career."