Uncharted 4: A Thief's End supports up to 10 players in its online multiplayer.
The multiplayer mode was built around competitive matches staged in settings adapted from the single-player campaign. Its standard team structure commonly placed five players against five, making 10 the total player capacity rather than the number on one team.
Uncharted 4 expanded the series' multiplayer formula with sidekicks, supernatural abilities called Mysticals, and customizable loadouts. Players could revive teammates, use grappling hooks, and fight across maps inspired by locations such as Madagascar and Scotland. The mode was available on the PlayStation 4 release.
The number is easy to confuse with the size of an individual team or with player counts from other online shooters. The relevant figure for this question is the full competitive match: two teams together can contain 10 players.