Sigma Alpha Iota was founded at the University School of Music in Ann Arbor, Michigan on June 12, 1903, to "form chapters of music students and musicians who shall by their influence and their musical interest uphold the highest ideals of a music education; to raise the standard of productive musical work among the women students of colleges, conservatories and universities."  The fraternity was founded by seven outstanding women: Elizabeth A. Campbell, Frances Caspari, Minnie Davis Sherrill, Leila Farlin Laughlin, Nora Crane Hunt, Georgina Potts, and Mary Storrs Andersen.

As of August 2024, SAI has 136,730 initiated members, 178 active collegiate chapters, and 115 active alumnae chapters including the International Chapter.