Paranoia [] (adjective: paranoid []) is a thought process believed to be heavily influenced by anxiety or fear, often to the point of irrationality and delusion. Paranoid thinking typically includes persecutory beliefs, or beliefs of concerning a perceived threat towards oneself. (e.g. "Everyone is out to get me.") Making false accusations and the general distrust of others also frequently accompany paranoia. For example, an incident most people would view as an accident or coincidence, a paranoid person might believe was intentional. However, just because an individual is paranoid does not necessarily mean his or her suspicions are false, as noted in Catch-22: "Just because you're paranoid doesn't mean they aren't after you."

Paranoia (also styled as PARANOIA) is a dystopian science-fiction tabletop role-playing game originally designed and written by Greg Costikyan, Dan Gelber, and Eric Goldberg, and first published in 1984 by West End Games. Since 2004 the game has been published under licence by Mongoose Publishing. The game won the Origins Award for Best Roleplaying Rules of 1984 and was inducted into the Origins Awards Hall of Fame in 2007.