A sea captain, also known as a ship's captain, captain, master, or shipmaster, is a high-ranking licensed mariner in charge of a commerce vessel.

The captain is in charge of the ship's seaworthiness, safety, and security, as well as cargo operations, navigation, crew management, and legal compliance, as well as the passengers and cargo on board.

Everyone on board, including government officials, crew, and passengers, are under the captain's command and are ultimately responsible to him, especially during navigation.

The captain is responsible for meeting the criteria of local immigration and customs officers on international voyages. Embarking and disembarking passengers, dealing with deserting crew members, making crew changes in port, and creating accommodations for foreign crew members are all examples of immigration concerns. A cargo declaration, a ship's stores declaration, a declaration of crew members' personal items, crew lists, and passenger lists are all possible customs procedures.