The Hydra class of ironclads composed three ships, Hydra, Spetsai, and Psara. The ships were ordered from France in 1885 during the premiership of Charilaos Trikoupis, as part of a wider reorganization and modernization of the Greek armed forces, which had proved themselves inadequate during the Cretan uprising of 1866. Launched in 1889 and 1890, the ships were ready for service with the Greek Navy by 1892. They were armed with a main battery of three 10.8-inch (274 mm) guns and five 5.9-inch (150 mm) guns, and had a top speed of 17 knots.

Hydra was an ironclad warship of the Greek Navy, named for Hydra, one of the Saronic Gulf islands which played a key role in the war at sea during the Greek War of Independence. The lead ship of her class of ironclads, she was ordered in 1885 in response to a crisis in the Balkans and Ottoman naval expansion. The ship was launched in 1889 and delivered to Greece by 1892. She was armed with a main battery of three 10.8 in (270 mm) guns and five 5.9 in (150 mm) guns, and had a top speed of 17 kn.