The Alagoas tyrannulet (Phylloscartes ceciliae) is a Critically Endangered species of bird in the family Tyrannidae, the tyrant flycatchers.

Their wings are blackish olive with thin yellowish green edges to the flight feathers.

Both sexes have a chestnut iris, a black bill, and dark bluish gray legs and feet.

It perches horizontally, sometimes with its tail cocked up, and makes short sallies to grab or hover-glean prey from leaves and twigs.

It makes a globular nest of plant fibers and dead leaves with a side entrance.

The clutch size, incubation period, time to fledging, and details of parental care are not known.

A very large percentage of its Atlantic Forest habitat has been cleared for timber and conversion to sugar cane plantations.