Diocaesarea or Diocaesareia or Diokaisareia (Ancient Greek: Διοκαισάρεια) was a Graeco-Roman town located in ancient Cappadocia near Nazianzus. According to Gregorius of Nazianzus, it was a small place. It is mentioned by Ptolemy and by Pliny the Elder.

Its site is located near Til (formerly Kaysar, reflecting the old name) in Asiatic Turkey.

 This article incorporates text from a publication now in the public domain: Smith, William, ed. (1854–1857). "Diocaesareia". Dictionary of Greek and Roman Geography. London: John Murray.

38°25′49″N 34°44′23″E / 38.4302975°N 34.7396455°E / 38.4302975; 34.7396455