Frigate lieutenant

Frigate lieutenant is a rank in some navies, especially those of Spain (Spanish: Alférez de Navío) and Latin America, roughly equivalent to a sub-lieutenant in the Royal Navy or a lieutenant (junior grade) in the US Navy. The French Navy equivalent is a ship-of-the-line ensign (first class) (French: enseigne de vaisseau de première classe).

The NATO rank code is OF-1 (senior)

Austria-Hungary
In the Austro-Hungarian Navy the rank of Fregattenleutnant or fregatthadnagy was the lowest rank of professional officers. It was superior to Korvettenleutnant (a reserve rank) and inferior to Linienschiffsleutnant. Until 1908 the rank was called Linienschiffsfähnrich (ship-of-the-line ensign).