The plain-crowned spinetail (Synallaxis gujanensis) is a species of bird in the Furnariinae subfamily of the ovenbird family Furnariidae.

It is found in Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, and Venezuela.

[2] The plain-crowned spinetail was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae.

Their crown and upperparts are dull brownish that is slightly grayer and darker on the forecrown.

S. g. inornata has richer brown upperparts than the nominate, with a buffier face and much brighter rusty underparts.

S. g. certhiola has a grayish face, a somewhat olivaceous back, a buffy white center to the belly, and wings, tail, and underparts that are intermediate between the rather plain nominate and the richly colored inornata.

[10][11][12][13][14] The plain-crowned spinetail's breeding season has not been defined but appears to vary geographically and in some areas be extended.

The species' nest is a globe of sticks that can be twice as long as it is wide, with a horizontal tunnel leading to the egg chamber.

[11] The song in Ecuador is rendered "a leisurely 'keé, kuh' repeated at several-second intervals".