The term top secret can be applied to information, actions, organizations, projects, etc. of which any knowledge is highly restricted or classified. Other uses:

• Top Secret (role-playing game) by TSR, Inc.
• Top Secret!, a 1984 film starring Val Kilmer
• A type of security clearance in the United States
• Top Secret (novel) a novel by John Reynolds Gardiner
• Top Secret Performance Engineering a Japanese motor vehicle tuning company