Juan Bermudo (c. 1510 in Écija, Province of Seville – c. 1565) was a Spanish Friar who is best known as a composer, music theorist and mathematician.

Bermudo entered the Franciscan Order in 1525. He was subsequently sent to study at the University of Alcalá, where he resided at the College of Saint Peter and Paul.  He then dedicated his energies to preaching to the people of that region.  The esteem he gained from the other friars of the province can be seen in his election on 24 June 1560 as a Definitor of the province.

After a period of illness Bermudo retired from his service as a preacher. During his recovery, he began to read various manuscripts of musical theory and cultivating his, as yet, untrained talents.

Bermudo’s first published work resulting from his studies was his Libro primero de la Declaración de instrumentos (1549), dedicated to King John III of Portugal.  It was soon followed by Comiença el Arte Tripharia.

In his Perfecting the perfect instrument of 1555, a treatise on playing the vihuela, Bermudo lists the maestro de capilla of the Royal Chapel of Granada, Bernardino de Figueroa, and Cristóbal de Morales as having checked and approved the text.