The Alagoas antwren (Myrmotherula snowi) is a Critically Endangered species of bird in subfamily Thamnophilinae of family Thamnophilidae, the "typical antbirds".

[6] The Alagoas antwren's specific epithet honors David Snow, a British ornithologist "who was a pioneer in life history studies of Neotropical birds".

It inhabits isolated fragments of semi-humid lowland evergreen forest and is known only from the narrow elevational range of 430 to 790 m (1,400 to 2,600 ft).

The researchers who determined that it was a species collected a female with an egg in its oviduct in February and noted juveniles with their probable parents in May.

The Alagoas antwren's song is an "irregular series of very high, sharp, drawn-out, well-separated 'seeup' notes, each 'seeup' descending".

The site continues to be threatened by fires spreading from adjacent plantations, hunting, timber extraction and agriculture."

Having a montane distribution that is close to the maximum altitude within its range, this species is also potentially susceptible to climate change".

[1] The 2021 paper's authors urged "actions to protect its nests, recompose mixed flocks, translocate individuals to nearby habitat patches, and attempt captive breeding, [are] among efforts that should be evaluated.