Fray Domingo de Santo Tomás, O.P. (1499 in Seville – 28 February 1570, in La Plata, Bolivia) was a Spanish Dominican and grammarian who compiled the first Quechua grammar.
He arrived in Peru in 1540 and founded the convent and city of Yungay on 4 August 1540. For the purpose of evangelization, he learned the Quechua language spoken along the coast near Lima. In 1545, he was elected prior of the Convento del Santísimo Rosario in Lima.In 1549 he made the "Tasa" of Lima, with Fray Jeronimo de Loayza and Fray Tomás de San Martín. In 1560 he published his Grammatica o arte de la lengua general de los indios de los Reynos del Perú in Valladolid, the first book printed in Quechua. In the same year appeared his Lexicon, o Vocabulario de la lengua general del PERV. The coastal dialect of Quechua was significantly different than that of Cuzco, which was described by Diego González Holguín in the early 17th century.