Lieutenant is a military, naval, paramilitary, fire service or police officer rank.
Lieutenant may also appear as part of a title used in various other organizations with a codified command structure. It often designates someone who is "second-in-command," and as such, may precede the name of the rank directly above it. For example, a "Lieutenant Master" is likely to be second-in-command to the "Master" in an organization utilizing both such ranks.