The Araguaia spinetail (Synallaxis simoni) is a species of bird in the Furnariinae subfamily of the ovenbird family Furnariidae.

Their tail is dark rufous; it is graduated and the feathers have blunt tips.

Their throat is white; their underparts are mostly tan with a whitish center on a paler belly.

It inhabits landscapes very near water including gallery forest, riparian woodland and scrublands, and river islands.

[3][7] The Araguaia spinetail's nest is a mass of sticks with a horizontal entrance tunnel placed near the ground in a shrub or small tree.

The Araguaia spinetail's song is a "single nasal downslurred note keeeu, repeated at intervals of 1‒3 seconds".

[1] It is considered fairly common "within its restricted range" and is protected in Cantão State Park.