Lookout boy aloft, by Harrison Weir

A lookout or look-out is a person on a ship in charge of the observation of the sea for hazards, other ships, land, etc. Lookouts report anything they see and or hear. When reporting contacts, lookouts give information such as, bearing of the object, which way the object is headed, target angles and position angles and what the contact is. Lookouts should be thoroughly familiar with the various types of distress signals they may encounter at sea.

A U.S. Navy sailor standing the lookout watch aboard a warship.

Naval application

Lookouts have been traditionally placed in high on masts, in crow's nests and tops.

The International Regulations for Preventing Collisions at Sea (1972) says in part:

Every vessel must at all times keep a proper look-out by sight (day shape or lights by eyes or visual aids), hearing (sound signal or Marine VHF radio) and all available means (e.g. Radar, ARPA, AIS, GMDSS...) in order to judge if risk of collision exists.

Criminal definition

By analogy, the term "lookout" is also used to describe a person who accompanies criminals during the commission of a crime, and warns them of the impending approach of hazards: that is, police or eyewitnesses. Although lookouts typically do not actually participate in the crime, they can nonetheless be charged with aiding and abetting or with conspiracy, or as accomplices.