A stiletto (Italian: [stiˈletto]) is a knife or dagger with a long slender blade and needle-like point, primarily intended as a stabbing weapon.

The stiletto blade's narrow cross-section and acuminated (tapering gradually to a sharp point) tip reduce friction upon entry, allowing the blade to penetrate deeply. Some consider the stiletto a form of dagger, but most stilettos are specialized thrusting weapons not designed for cutting or slashing, even with edged examples.

Over time, the term stiletto has been used as a general descriptive term for a variety of knife blades exhibiting a narrow blade with minimal cutting surfaces and a needle-like point, such as the U.S. V-42 stiletto, while in American English usage, the name stiletto can also refer to a switchblade knife with a stiletto- or bayonet-type blade design. The term in (Anglicised) plural "stilettos", is also used as slang for footwear (boots or shoes) exhibiting thin, high “stiletto” heels.