The Olivaceous Woodcreeper (Sittasomus griseicapillus) is a passerine bird which breeds from southern Mexico through tropical Central and South America to northern Argentina, and also on Tobago. The species is throughout the Amazon Basin, but is absent from the lowest reaches of the basin, including much of the adjacent Guyanas. It is the only member of the genus Sittasomus, but the taxon includes several vocally and morphologically distinct forms, so this species may be split in the future.

This small woodcreeper is a slender bird, typically 15cm long, and weighing 13g. The head, upper back and underparts are greyish olive, and the wings, tail and lower back are light rufous. The bill is short and thin. The normal call is a fast, high-pitched trill wu-wu-wu-we-we-we-we-ee-ee-ee-ee-we-we-we-we.

The Olivaceous Woodcreeper is a common and widespread bird of forests and other woodlands. The Olivaceous Woodcreeper feeds on insects and spiders. It normally forages on tree trunks or large branches or on the ground, usually alone. However, birds associate with foraging groups of Golden Lion Tamarins (Leontopithecus rosalia) to snatch prey startled by the monkeys.

It builds a nest lined with dead leaves in a tree hole, and lays three white eggs.