The end-of-season tournament starts in Turin on Sunday, November 12, with Novak Djokovic the top seed and Carlos Alcaraz the second seed.
Djokovic has been put in the Green Group alongside Jannik Sinner, Stefanos Tsitsipas and Holger Rune.
Alcaraz leads the Red Group with Daniil Medvedev, Andrey Rublev and Alexander Zverev.
Djokovic and Alcaraz will be favourites to advance to the semi-finals, but what will be the key matches in deciding who makes it out of the groups?
We look at four of the key contests.
Sinner v Tsitsipas
Will Sinner be the biggest challenger to Djokovic in the Green Group?
The Italian has been in improving form over the last third of the season, beating Medvedev and Alcaraz to win the title in Beijing, then beating Medvedev again in the final in Vienna.
On home turf he should fancy his chances of at least making the semi-finals, despite not having a winning record against anyone in the group.
He is 0-2 against Rune, 2-5 against Tsitsipas and 0-3 against Djokovic.
The Tsitsipas match-up is interesting as Sinner had lost four in a row before beating Tsitsipas in straight sets in Rotterdam earlier this year. That was an indoor hard-court match and Sinner will be hoping for a repeat to give his semi-final chances a boost.
Rune v Tsitsipas
Rune could be the one to watch out for in the Green Group.
He has a 2-2 record against Djokovic and leads the head-to-head 2-0 against both Sinner and Tsitsipas.
A few weeks ago the mood around Rune might have been different, but the addition of Boris Becker to his coaching team has made an immediate impact.
When he beat Tsitsipas in their last meeting, which was indoors in Stockholm in 2022, Rune said he played “very close to perfection”.
If he can find that level again he will be a tough opponent for Tsitsipas, who has found a bit of form over the last month but might still have his work cut out to make it out of this group.
Alcaraz v Medvedev
It looked like Alcaraz had Medvedev’s number after beating him in straight sets in the Indian Wells final and Wimbledon semi-finals.
He also has a good record at the ATP Finals.
Last year he was somewhat unlucky not to make it out of the group stage after three successive three-set defeats that were all decided by a tie-breaker, but in 2021 he made the final, and in 2020 he lifted the trophy.
This is arguably the standout match of the group stage and will likely decide who finishes top.
Alcaraz v Rublev
This is an intriguing match-up for a few reasons.
Firstly these two players have never met on the ATP Tour. The only time they faced off was in an exhibition match in December 2022.
Rublev ran out a 6-2 6-1 winner on that occasion as his power hitting proved too hot to handle for Alcaraz.
There’s probably not too much to be read into that result as Alcaraz was returning from a six-week injury lay-off, but Rublev definitely has the weapons to give the world No. 2 a stiff test.
Were Alcaraz to lose to Rublev it would open up the group and give possibilities for a potential surprise semi-finalist.