Istros the Callimachean was a Greek writer, probably from Paphos. He was a pupil of Callimachus, and active in the Library of Alexandria. Seventy-seven fragments of his writings remain, mostly from his four-volume Attica, which discussed the cult, religion, and institutions of Attica in its mythical past, based largely on Atthides. According to the Suda, a 10th-century encyclopedia, he wrote both prose and verse.