Minimum Players for Solitaire: One

One. By definition, Solitaire (Patience) is a single-player card game. The minimum and maximum number of players is 1.

If you play with others, it becomes a different activity: competitive Patience (racing separate layouts), cooperative Solitaire (shared tableau), or a multiplayer game like Spit / Speed (simultaneous shedding). But classic Solitaire = 1 player.