Tin hat

Tin hat can refer to:
 * Kettle hat, part of medieval armour
 * Tin hat (military), the Brodie helmet of World Wars one and two (which is also the origin of the UK phrase "put the tin hat on [something]")

As a proper noun, Tin Hat can refer to:
 * Tin Hat Linux, a Linux distribution
 * Tin Hat, formerly known as the Tin Hat Trio, an acoustic chamber music group currently based in San Francisco, California