The maximum number of players in a standard Versus match in Super Smash Bros. Ultimate is 8.
Ultimate expanded the series’ local multiplayer scale beyond the four-player limit used by earlier mainline entries. On one Nintendo Switch, up to eight fighters can take part in a standard battle when the selected rules, stage, and controller setup support that many participants. Players can compete individually or divide into teams.
The eight-player limit applies to local multiplayer and is separate from the number of people who may participate in tournament brackets or other modes. Ultimate’s Tournament mode, for example, can handle up to 32 entrants, but those entrants do not all fight simultaneously in one standard match. Online play also uses different limits and conditions, so online player counts should not be used to answer this question.
The match can use Timed, Stock, or Stamina rules, along with items, stage hazards, and team settings. With eight fighters on screen, the action becomes especially chaotic, which is why many players use larger stages or reduce items when organizing eight-player sessions.