Des Murs's Wiretail (Sylviorthorhynchus desmursii) is a small passerine bird of southern South America which belongs to the ovenbird family Furnariidae. It is the only member of the genus Sylviorthorhynchus. Molecular phylogenetics places it within the Synallaxinae and indicates that the genus diverged from the Leptasthenura about 14-15 million years ago.

It is 24 cm long, with the very long tail accounting for about two-thirds of this. The tail consists of just six feathers which are very narrow and filament-like. The two central feathers are greatly elongated while the two outer feathers are very short. The plain plumage is reddish-brown above, paler on the underparts. There is a pale stripe above the eye. The bird is small and rounded with a very fine bill. The song is fast and high-pitched.

It is found in western Argentina from Santa Cruz Province north to San Juan and in southern and central Chile from northern Magallanes to Valparaíso Region. It inhabits dense thickets of Chusquea bamboo within cool temperate rainforests, occurring from sea-level up to 1,200 metres. It is very shy and difficult to see.

The ball-shaped nest is made of plant fibres and built amongst vegetation close to the ground.