The plain-mantled tit-spinetail (Leptasthenura aegithaloides) is a small passerine bird of South America in the Furnariinae subfamily of the ovenbird family Furnariidae.

The South American Classification Committee of the American Ornithological Society, the International Ornithological Committee, and the Clements taxonomy assign it these four subspecies:[3][2][4] However, BirdLife International's Handbook of the Birds of the World (HBW) treats L. a. berlepschi as the separate species "buffy tit-spinetail" and L. a. pallida as another separate species, the "pallid tit-spinetail".

Adults of the nominate subspecies L. a. aegithaloides have a white supercilium on an otherwise dark brownish, whitish streaked, face.

Juveniles have indistinct crown and throat markings, a lightly spotted back, and rounded tail feathers.

It has a paler cinnamon crown whose streaks greatly contrast, pale buff streaks on the neck, cinnamon rather than rufous on the wing coverts and flight feathers, pale buff outer tail feathers, and entirely buffy underparts.

[6][7] The nominate subspecies of the plain-mantled tit-spinetail is found in central Chile between the Coquimbo and Aysén regions.

Subspecies L. a. grisescens is the northernmost; it is found coastally from Peru's Department of Arequipa south into northern Chile as far as the Atacama Region.

L. a. berlepschi is found in the Andes of southern Peru, northern Chile, western Bolivia, and northwestern Argentina.

The nominate subspecies and L. a. grisescens occur in arid scrublands (both lowland and montane), open forests, and in the natural vegetation in human-modified areas like agricultural fields, parks, and oases.

L. a. pallida inhabits scrublands and woodlands at the transition between the lower elevation forest and higher steppe; it also occurs on salt flats and in arid thorny woods.

The southern sub-population of L. a. pallida moves north as far as central and northern Argentina, but the details of its migration are not well understood.

The nominate subspecies' song is "a high-pitched descending, broken trill lasting 2–5 seconds, with accentuated sharper notes, e.g. 'chikiti-chikiti-chikiti- chikiti-ti-ti-ti-pweew-ti-ti-ti-pweew-ti-ti-ti…' ".

[6] The IUCN follows HBW taxonomy and so has separately assessed the "plain-mantled" sensu stricto, the "buffy", and the "pallid" tit-spinetails.