HY´DREA(Ὑδρέα: Eth. Ὑδρεάτης: Hydra), a small island off the coast of Hermionis and Troezenia. It originally belonged to the inhabitants of Hermione, who gave the island to the Samian exiles instead of money, and the latter pawned it to the Troezenians. (Hecat ap. Steph. B. s. v.;Hdt. 3.59; Paus. 2.34.9.) Hydrea, which is rarely mentioned in antiquity, became in modern times the head-quarters of Grecian commerce and the cradle of modern Grecian freedom. Although Hydrais only a few miles in circumference, so rocky as scarcely to yield the common vegetables, and with no water except what is collected in cisterns, it attained by its commerce an extraordinary degree of prosperity. Before the Greek revolution it had a wealthy population of more than 25,000 souls, and upwards of 300 trading vessels. But the losses which the Hydriotes experienced gave a blow to their prosperity from which they have never recovered. (Holland, Travels, vol. 2. p. 202, 2nd ed.; Boblaye, Recherches, &c. p. 63; Leake, Peloponnesiaca, p. 284, seq.; Curtius, Peloponnesos, vol. 2. p. 456.)