Multiplayer games revolve around playing with other people. Matchmaking systems solve the problem of players having a hard time finding others to play with in multiplayer online games. It is often impractical to find the people to play a match of a game together—matchmaking systems provide the glue for these gameplay experiences to happen. The chapter discusses queue systems and analytics to monitor queues. Most design changes to other parts of the matchmaking system will impact how players are removed from, remain in, or get returned to queues, causing queue design to be a core component of moving players from starting up a game to entering a match. Queues are the entry point for players into the matchmaking system, maintaining a list of parties seeking matches and moving them into matches. Games often have multiple queues: in HotS each game mode has a separate queue of players.