For alternate meanings see Edmonton Oilers and Houston Oilers

An oiler is a ship, also called a tanker, that can carry a liquid cargo of petroleum, or a naval support vessel that carries fuel to naval ships at sea, and can transfer the fuel during underway operations.

In the United States Navy, oilers carry the designation AO. They can carry small quantities of ammunition, cargo, and provisions.

An oiler is also a person, or a job title of a person, who works at keeping machinery lubricated, such as within the engine compartment of a ship.