Ship-of-the-line lieutenant is a common naval rank, equivalent to the naval rank of Lieutenant in the UK, Commonwealth and US.

The name of the rank derives from the name of the largest class of warship, the ship of the line

Ship of the line

A ship of the line was a type of naval warship constructed from the 17th through the mid-19th century to take part in the naval tactic known as the line of battle, in which two columns of opposing warships would manoeuvre to bring the greatest weight of broadside guns to bear...

, as opposed to smaller types of warship (corvettes and frigates).

The rank is lieutenant de vaisseau in French, tenente di vascello in Italian and teniente de navio in Spanish.

The NATO rank code is OF-2.