Seaman Jacob Gibson pilots a rigid-hull inflatable boat from the amphibious transport dock USS Ponce (LPD 15)

Seaman is one of the lowest ranks in a navy. In the Commonwealth it is the lowest rank in the navy, followed by able seaman and leading seaman, and followed by the petty officer ranks.

In the United States, it means the lowest three enlisted rates of the U.S. Navy, followed by the higher petty officer ranks. The equivalent of the seaman, in French-speaking countries, is the matelot.

The term "seaman" is also a general-purpose for a man or a woman who works anywhere on board a modern ship, including in the engine spaces, which is the very opposite of sailing. Furthermore, "seaman" is a short form for the status of an "able-bodied seaman", either in the navies or in the merchant marines. An able-bodied seaman is one who is fully trained and qualified to work on the decks and superstructure of modern ships, even during foul weather, whereas less-qualified sailors are restricted to remaining within the ship during times of foul weather — lest they be swept overboard by the stormy seas or by the high winds.