Marsilius of Padua (Italian Marsilio or Marsiglio da Padova; born Marsilio dei Mainardini or Marsilio Mainardini, c. 1275 – c. 1342) is an Italian scholar, trained in medicine who practiced a variety of professions.

He is also an important fourteenth century political figure.

His political treatise Defensor pacis, a promotion of virtually unlimited monarchical power, especially in regard to the Church, is seen by some authorities as the most revolutionary political treatise written in the later Middle Ages.

It is one of the first examples of a reasoned defense of caesaropapism in Western Europe.