Giovanni Battista Doni (c. 1593 – 1647) was an Italian musicologist who made an extensive study of ancient music. Known, among other works, for having changed the name of note Ut (C) renaming it Do after his own family name to ease solfege.
Born in Florence, he studied Greek, rhetoric, poetry and philosophy at the Universities of Bologna and Rome. He received the degree of doctor from the University of Pisa and was chosen to accompany Cardinal Neri Corsini to Paris in 1621 where he became acquainted with Marin Mersenne and other literary persons.
On returning to Florence in 1622, he entered the service of Cardinal Francesco Barberini, and went with him to Rome where Barberini became Dean of the College of Cardinals, afterwards accompanying the cardinal to Paris, Madrid, and back to Rome. Doni made good use of the opportunities that came his way on those journeys, to acquire exhaustive knowledge of ancient music. Among other things, he invented, or reconstructed, a double lyre which, in honour of his patron, he called a Lyra Barberina or Amphichord (see barbiton).
After the death of his brother, he returned to Florence around 1640, where he married and settled down as professor at the university.