Semystra (Ancient Greek: Σημύστρα) was a town of ancient Thrace. Dionysius of Byzantium wrote that there was an altar of the nymph Semystra there, whence the name of the town. Semystra was a nymph, she nurtured the Keroessa, who was the daughter of Io and Zeus. Dionysius added that Semystra nearly became a big city during the Greek colonization, since the leaders of the colonization tried to found the city, but during the sacrifices, a crow snatched one of the thighs from the middle of the flames and carried it to the Bosporion promontory. The rest of the Greeks saw this as a sign from Apollo and went to the spot were the crow left the thigh.
- Richard Talbert, ed. (2000). Barrington Atlas of the Greek and Roman World. Princeton University Press. p. 53, and directory notes accompanying.
- Dionysius of Byzantium, Anaplous of the Bosporos, §24
- Anaplous Bosporou. Dionysii Byzantii De Bospori navigatione quae supersunt; una cum supplementis in geographos graecos minores aliisque ejusdem argumenti fragmentis e codicibus MSS. edidit Carolus Wescher, p.12
- Lund University. Digital Atlas of the Roman Empire.