Theodoros or Theodorus (Greek: Θεόδωρος) is a masculine given name, from which Theodore is derived. The feminine version is Theodora. It may refer to:

Ordered chronologically

• Theodorus of Samos, 6th-century BC Greek sculptor, architect and inventor
• Theodorus of Cyrene, 5th-century BC Libyan Greek mathematician
• Theodorus of Byzantium, late 5th-century BC Greek sophist and orator
• Theodorus the Atheist (c. 340–c. 250 BC), Libyan Greek philosopher
• Theodorus of Athamania (fl. 225 BC), King of a tribe in Epirus
• Theodorus (meridarch) (fl. 100–55 BC), civil governor of the Swat province of the Indo-Greek kingdom
• Theodorus of Gadara, 1st-century BC Greek rhetorician
• Theodorus of Asine (fl. 3rd–4th century), Greek Neoplatonist philosopher
• Theodorus of Tabennese (c. 314–368), Egyptian Christian monk
• Theodorus (usurper) (fl. 372), Roman usurper against Emperor Valens
• Theodorus Priscianus, 4th-century physician at Constantinople
• Theodorus I (bishop of Milan) (died 490)
• Theodorus (consul 505) (fl. 505–523), Roman politician
• Theodorus Lector (fl. 520-530), Byzantine scholar and historian
• Theodore Rshtuni (590-654/655), Armenian nobleman who fought against the first Arab invasions of Armenia
• Theodorus (archbishop of Ravenna) (died 691)
• Pope Theodoros I of Alexandria, 45th Coptic Pope of Alexandria and Patriarch of the See of St. Mark (730–742) (also known as Theodosius II)
• Saint Theodorus (c. 775–c. 842), monk from Jerusalem
• Theodore Balsamon, 12th-century Eastern Orthodox Patriarch of Antioch
• Theodore I Laskaris, Emperor of Nicaea (1204–1221 or 1205–1222)
• Theodore II Laskaris, Emperor of Nicaea (1254–1258)
• Theodore Hyrtakenos (fl. 1300), Byzantine court official and writer
• Theodore II Palaiologos (c. 1396–1448), Despot in the Morea
• Theodoros Pelecanos of Corfu (fl. 1478), Greek scribe

Ordered by last name, where available

• Pope Tawadros II of Alexandria (born 1952), current Coptic Pope of Alexandria and Patriarch of the See of St. Mark
• Patriarch Theodore II of Alexandria (born 1954), current Eastern Orthodox Patriarch of Alexandria and all Africa
• Theo Angelopoulos (1935–2012), Greek filmmaker, screenwriter and producer
• Theodorus Bailey (politician) (1758–1828), United States senator from New York
• Theodorus Bailey (officer) (1805–1877), United States Navy rear admiral
• Theodorus W. Brevard (1804–1877), American comptroller
• Theodorus Frederik van Capellen (1762–1824), Dutch naval officer
• Theodorus van der Croon (1668–1739), Dutch Archbishop of Utrecht
• Theodorus Dekker (1927–2021), Dutch mathematician
• Theodoros Deligiannis (1820–1905), Greek politician, five times Prime Minister of Greece
• Theodorus Jacobus Frelinghuysen (c. 1691–c. 1747), German-American minister and theologian
• Theodorus Jacobus Frelinghuysen II (1724–1761), New York theologian
• Theodorus Janssonius van Almeloveen (1657–1712), Dutch physician
• Theodorus Klompe (1903–1963), Dutch geologist
• Theodoros Kolokotronis (1770–1843), Greek general and preeminent leader of the Greek War of Independence
• Theodorus van Kooten (1749–1813), Dutch poet, professor and politician
• Theodorus B. M. Mason (1848–1899), American founder of the Office of Naval Intelligence
• Theodorus Bailey Myers (1821–1888), American collector of books and historical manuscripts
• Theodoros Natsinas (1872–1949), Greek teacher
• Theodoros Negris (1790–1824), Greek politician
• Theodorus Netscher (1661–1728), Dutch painter
• Theodoros G. Orphanides (1817–1886), Greek botanist
• Theodoros Pangalos (general) (1878–1952), Greek general, dictator in 1925–26
• Theodoros Pangalos (politician) (1938–2023), Greek politician, foreign minister and deputy prime minister of Greece
• Theodoros Papagiannis (born 1942), Greek sculptor
• Theodoros Papaloukas (born 1977), Greek basketball player
• Theodorus Marinus Roest (1832–1898), Dutch numismatist
• Theodorus Marinus Roest van Limburg (1806–1887), Dutch journalist, diplomat, and politician
• Theodoros Roussopoulos (born 1963), Greek politician
• Theodorus Johannes Schoon (1915–1985), Dutch-New Zealand artist, photographer and carver
• Theodorus Schrevelius (1572–1649), Dutch writer and poet
• Theodorus Skuminowicz (died 1668), Lithuanian Bishop of Vilnius
• Theodoros Stamos (1922–1997), Greek-American painter
• Theodoros Tripotseris (born 1986), Greek footballer
• Theodoros Tzinis (1798–1869), Greek fighter in the Greek War of Independence
• Theodoros Vasilakakis (born 1988), Greek footballer
• Theodoros Velkos (born 1976), Greek badminton player
• Theodoros Voutiritsas (born 1962), Greek football manager and former player
• Theodoros Vryzakis (1819–1878), Greek painter
• Theodoros Zagorakis (born 1971), Greek politician and former footballer
• Theodoros Ziakas (1798–1882), Greek fighter in the Greek War of Independence

• James Bass Mullinger (1834 or 1843–1917), British author who sometimes used "Theodorus" as a pen name