Senior Assassin, also known as Senior Tag, Killer Game, and Catcher Games, is a live-action game commonly played by high school seniors and university students. The game consists of a group of high school seniors who are all assigned targets anonymously, and the point of the game is for an assassin to eliminate their target. Players can use any form of water to eliminate a target, like a water balloon or a water bottle, but most just use a plastic water gun. After being assigned a target, their assassin has three days to eliminate them. Every player must contribute money for a chance at the pot, which is usually around $1000. The game lasts for several weeks, and the last person standing wins the pot.

Senior Assassin has been played at many schools for decades, and it has appeared in multiple works of popular culture, including feature films and TV series like Gossip Girl, Community, and iCarly. During the Senior Assassin season, social media is flooded with funny videos of players catching their targets in creative and sometimes unbelievable ways. The game is a way to create lasting memories with friends and foes.

However, Senior Assassin has led to multiple debates and controversies, partly due to its name. Many school faculty and staff say that the name Senior "Assassin" is very inappropriate, in light of recent school shootings across America. Some schools have banned the game due to safety concerns, as players have been known to dress in dark clothing and sneak through residential areas as part of the game. Despite these concerns, Senior Assassin remains a beloved tradition among students around the world.