The Transvolcanic jay (Aphelocoma ultramarina) is a bird endemic to Mexico.

It is a medium-large (~120 g) passerine bird similar in size to most other jays, with a blue head, blue-gray mantle, blue wings and tail, gray breast and underparts.

The sexes are morphologically similar, and juveniles differ only in having less blue coloration.

It is most readily distinguished by the plain (unstreaked) throat and breast, and the mantle contrasting less with the head and wings.

A 2011 decision by the American Ornithologists' Union Check-list Committee treats some populations of the Mexican jay as a separate species, called the Transvolcanic jay (A. ultramarina), based on diagnosable phenotypic differences in plumage and morphology, millions of years of genetic divergence, and no evidence for interbreeding with Mexican Jays.