Theoctistus or Theoktistos (Greek: Θεόκτιστος) is a Greek name derived from θεος theos, "god", and κτίσμα ktisma, "creation, edifice, foundation", the resulting combination being translated to "creation of God", "godly creation".

Theoctistus or Theoktistos can refer to, chronologically:

• Theoctistus of Caesarea (2nd-3rd centuries), bishop; see Origen
• Theoctistus of Alexandria (3rd century), a sea captain, martyr, saint, and companion of Faustus, Abibus and Dionysius of Alexandria (martyred 250)
• Theoctistus of Palestine (died 451 or 467), aka Venerable Theoctistus (Theoktistos) of Palestine, Byzantine monk, hermit and Orthodox saint, active in Palestine, companion of Saint Euthymius the Great with whom he established a monastery, commemorated on September 3
• Monk Theoktistos (died 800), the hegumen of Sicilian Kucuma, commemorated as an Eastern Orthodox saint.
• Theoktistos (magistros) (fl. 802–821), senior Byzantine official
• Theoctistus of Naples, Duke of Naples in 818-821
• Theoktistos Bryennios (fl. ca. 842), Byzantine general
• Theoktistos, chief minister and regent of the Byzantine Empire from 842 to 855
• Theoktistos the Stoudite, 14th-century Byzantine ecclesiastical writer
• Teoctist I of Moldavia (ca. 1410 – 1477), Metropolitan of Moldavia from 1453 to 1477
• Teoctist Arăpaşu (born Toader Arăpaşu; 1915–2007), Patriarch of the Romanian Orthodox Church from 1986 to 2007
• Teoctist Blajevici (1807–1879), Metropolitan of Bukovina and Dalmatia