A telnyashka (Russian: Тельняшка) is a dark color and white striped, sleeveless or not, undershirt, which is an iconic uniform of the Russian Navy, the Russian Airborne Forces (VDV) and the Russian Naval Infantry (marines), initially by Soviet predecessors of these troops. It has been a symbol of great military pride for those who wear it gradually becoming a broader symbol of masculinity and self-confidence.

The official uniforms of mentioned troops include no shirts and a specially crafted jacket thus making telnyashkas a visible part of it (not just underwear).

Telnyashkas are also available to civilian customers and may come in a variety of knittings. Single thread knitting is the standard military-issue variant, but double and quadruple knittings for increased warmth can be produced. A quadruple telnyashka is enough to keep a person warm with nothing else on even at 5°C, as it was originally developed for military divers to be worn under a dry suit.^{[citation needed]}

Telnyashkas come from a practice that originated in the merchants and fishermen of Brittany, who adopted the style to distinguish them from other nationalities at a distance, later adopted and popularized by the French Navy and other navies of the pre-Dreadnought era. These continued in use for some time.