Diego Collado (c. 1587–1638 or 1641) was a Spanish Dominican missionary and linguist who played a notable role in early European efforts to document the Japanese language. Born in Miajadas, Spain, Collado entered the Dominican Order in Salamanca around 1600. In 1619, he traveled to Japan, where Christianity had already been outlawed by the Tokugawa shogunate. Operating in secret, Collado spent several years in hiding, frequently changing residences to evade arrest while learning the local language and proselytizing to the Japanese population.
After being recalled to Europe in 1622, Collado spent the next decade actively contesting the Jesuit monopoly on missionary work in Japan. He criticized what he viewed as the venal behavior of the Jesuits, contributing to the ongoing rivalry between the Dominican and Jesuit orders. During his time in Rome, Collado focused on preparing future missionaries by publishing linguistic aids. In 1632, he released a Japanese grammar, a vocabulary, and a confessionary, which represented the first such works translated into Ecclesiastical Latin.
Collado returned to Asia in 1635, but his strident views and advocacy for a new mission to Japan created friction with established Dominican authorities in the region. Rebuked and ordered to return to Spain, his journey was cut short when his ship capsized off the coast of the Philippines, resulting in his death by drowning.
