Tennis's season-ending championship is the oldest of the sport's marquee non-major titles, founded in 1970 as the Masters Grand Prix and reshaped repeatedly since — the Tennis Masters Cup, the ATP World Tour Finals at London's O2 from 2009 through 2020, and now simply the ATP Finals, staged on indoor hard at Turin's Inalpi Arena since 2021. It closes the calendar in mid-November, after the Masters 1000 hardcourt run through Shanghai and Paris, serving as both year-end trophy and a ledger on who actually earned a place at the top.
What separates it from the four Slams is structure. There is no draw to fall into and no early-round cushion: the top eight singles players from the season's race split into two round-robin groups, each man guaranteed three matches before a single elimination round trims the field to a semifinal four. A player can lose a match and still lift the trophy; a player can win two matches and go home on a games-percentage tiebreak. The indoor hard court rewards flat, first-strike tennis — big serving, short points, no wind or sun to manage — which makes it a fundamentally different test from the slower outdoor swings that precede it.
The Turin era has belonged to the game's clay-and-grass headliners adapting to a fast roof, with the championship repeatedly settled between the names who also contest the majors — the same cohort led now by Jannik Sinner and Carlos Alcaraz, with Alexander Zverev and Novak Djokovic among the multiple-time qualifiers who have shaped its modern finals.
Turin holds hosting rights into the back half of the decade, and the eight-man, no-second-chances format remains the event's defining signature: a week where the season's hierarchy is confirmed or overturned without the margin a Slam draw allows.