A tam o' shanter (in the British military often abbreviated to ToS) is a name given to the traditional Scottish bonnet worn by men. The name derives from Tam o' Shanter, the eponymous hero of the 1790 Robert Burns poem.

The tam o' shanter is a flat bonnet, originally made of wool hand-knitted in one piece, stretched on a wooden disc to give the distinctive flat shape, and subsequently felted.