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.

[3] Hydra was ordered from the Ateliers et Chantiers de la Loire shipyard in St. Nazaire, France during the premiership of Charilaos Trikoupis.

The ship, named for the island of Hydra, was launched in 1889, and by 1892, she and her sister-ships Spetsai and Psara were delivered to the Greek fleet.

The Ottoman Navy had remained in port during the conflict, but a major naval intervention of the Great Powers prevented the Greeks from capitalizing on their superiority.

[8] Two months later, the Ottoman fleet attacked the Greek navy, in an attempt to disrupt the naval blockade surrounding the Dardanelles.

[9] The Ottoman fleet, which included Turgut Reis, Barbaros Hayreddin, two outdated ironclad battleships, nine destroyers and six torpedo boats, sortied from the Dardanelles at 9:30.

The Greek flotilla, which included the armored cruiser Georgios Averof and Hydra and her sisters, had been sailing from the island of Imbros to the patrol line outside the straits.

At 10:04, the Ottoman ships completed a 16-point turn, which reversed their course, and steamed for the safety of the straits in a disorganized withdrawal.

[9] The Naval Battle of Lemnos resulted from an Ottoman plan to lure the faster Georgios Averof away from the Dardanelles.

[11] At the outbreak of World War I in at the end of July 1914, Greece's pro-German monarch, Constantine I, decided to remain neutral.

[7] In October 1916, Hydra and a pair of torpedo boats defected to the Venizelist faction in the National Schism.