A platoon leader (NATO) or platoon commander (more common in Commonwealth militaries and the US Marine Corps) is the officer in charge of a platoon. This person is usually a junior officer – a second lieutenant or first lieutenant or an equivalent rank. The officer is usually assisted by a platoon sergeant. Some special units, such as specific aviation platoons and special forces, require a captain as platoon leader, due to the nature and increased responsibility of such assignments. Platoons normally consist of three or four sections (Commonwealth) or squads (US).

The duties and responsibilities of a platoon leader is similar in the armies. Based on the US Army publications, it is possible to address that a platoon leader:

In Mechanized infantry units, also, the platoon leader:

While the rank is used in some NATO countries, it is ranked differently depending on the country.