Who are the youngest champions in the ATP Tour era?

Joao Fonseca won his first ATP Tour title on Sunday at the IEB+ Argentina Open. The Brazilian lifted the trophy aged 18 years, five months and 26 days, which made him the youngest South American to claim glory in the ATP Tour era (since 1990).

No younger South American has claimed a tour-level crown since Guillermo Perez-Roldan won Buenos Aires in 1987. Fonseca defeated Francisco Cerundolo in straight sets in the ATP 250 championship clash.

Who are the youngest champions in the ATP Tour era overall? Lleyton Hewitt became the youngest when he triumphed at Adelaide in 1998 aged 16 years, 10 months, 18 days.

Youngest Champions in ATP Tour era (since 1990)

Fonseca slotted in at 10th on the list, winning at a younger age than former No. 1 in the PIF ATP Rankings Pete Sampras, who earned his first ATP Tour title in Philadelphia 35 years ago.

Only Lleyton Hewitt, Andrei Medvedev, Kei Nishikori, Rafael Nadal, Carlos Alcaraz and Michael Chang have taken home a trophy at a younger age than Fonseca since 1990. All six players reached a career-high PIF ATP Ranking inside the world's top four.

The only active players in the Top 10 on the youngest champions leaderboard (since 1990) besides Fonseca are Kei Nishikori, who won in Delray Beach in 2008 (18 years, one month, 19 days) and Carlos Alcaraz, who emerged victorious four years ago in Umag (18 years, two months, 20 days).