This dissertation develops a methodology for understanding tonality and tonal structures in Renaissance polyphony by exploring the ways that the modern-day analyst and listener experience tonal phenomena in this music through a historically-informed lens. Regarded as one of the most important composers of the late-sixteenth century, Tomás Luis de Victoria (c. 1548–1611) and his compositions offer an excellent laboratory for the investigation of tonal practices in Renaissance polyphony as his repertoire solely consists of sacred vocal polyphony, providing a consistent compositional style and removing the need for any stylistic considerations of secular or instrumental music.