nauarch, in ancient Greece, an admiral or supreme commander of the navy, used as an official title primarily in Sparta in the late 5th and early 4th centuries bc. The Spartan nauarch could hold office only once, for a period of one year, and being subject to the highest magistrates, the ephors, could be deposed if proved incompetent. Acting independently of the kings and hampered by no colleague, however, the nauarch exercised considerable power and influence.