The Mishana tyrannulet (Zimmerius villarejoi) is a species of bird in the family Tyrannidae, the tyrant flycatchers.

[4] The Mishana tyrannulet's common name is from the Zona Reservada Allpahuayo-Mishana in the Department of San Martín, where the holotype was collected.

Its specific epithet is "in honor of the Augustinian priest P. Avencio Villarejo (1910–2000)" who traveled the Peruvian Amazon in the 1930s and 1940s and described its flora, fauna, and the customs of its indigenous peoples.

Both populations primarily inhabit scrubby or low-stature forest on nutrient-poor white sand soils.

It feeds mostly in the forest subcanopy and canopy, actively moving about and gleaning food while perched and taking arthropods with brief sallies to leaves and twigs.

During the day it commonly makes "a closely spaced pair...of thin, rising (about 4.5–5.5 kHz), whistled notes".

It occasionally makes "a more complex, multisyllabic...descending series (about 4.5–3.5 kHz) in which both the notes and the internote intervals become successively shorter through the first half".

[5] The vocalizations of the San Martín population are similar "but begin with a much stronger initial downward component".