A naval division is a subdivision of a squadron or flotilla. It can also be a subdivision of a fleet. A division is the smallest naval formation, most commonly numbering between two and four ships.
A division is usually commanded by senior flag officer, most commonly a vice admiral or rear admiral, irrespective of the division's size. For example, in the Imperial Japanese Navy the First Carrier Division was commanded by a rear or vice admiral, same as the 18th Cruiser Division.
Divisions are most commonly grouped by ship class and type, dependent on how the respective nation's navy is organised. Examples of division types include: