The Greco-Roman name Dionysius, deriving from the name of the god Dionysos or Dionysus, was exceedingly common, and many ancient people, famous and otherwise, bore it. It remains a common name today in the form Dennis (Denys, Denis).
Among the historical figures known by the name Dionysius, some of the more famous were:
- Dionysius the Elder (or Dionysius I), a ruler of Syracuse in Sicily
- Dionysius the Younger , (or Dionysius II), son of the preceding, more famous than his father, the quintessential Graeco-Roman tyrant
- Dionysius Periegetes, Greek geographer, 3d century BC
- Dionysius Thrax, Greek grammarian, 2d century BC
- Dionysius the Areopagite, a citizen of Corinth who was converted by Paul of Tarsus
- Dionysius of Halicarnassus, a Greek historian of the Roman period
- Saint Dionysius of Alexandria, an Egyptian bishop of the 3d century
- Saint Denis, Bishop of Paris, martyr (died ca. 250)
- Pope Dionysius
- Pseudo-Dionysius the Areopagite, identified by some with a Georgian theologist Peter the Iberian (411‑491), author of Corpus Areopagiticum
- Dionysius Exiguus, a Dacian monk who helped set the date of some Christian holidays
- Dionysius Telmaharensis, a former head of the Syrian Jacobite Church
- Dionysius the Wise, the Russian medieval icon-painter
- Dionysius I, Metropolitan of Moscow, a 14th century orthodox prelate
- Benjamin Musaphia, Jewish doctor, scholar, and kabbalist (1606-1675), who sometimes called himself Dionysius.
- Dionysius Lardner, an Irish scientific writer
