Fregate lieutenant) was an officer rank in the Austro-Hungarian Navy.

Pertaining to the modern day's NATO rank code it could be comparable to OF-1a (senior).

It was superior to Korvettenleutnant (a reserve rank) and inferior to Linienschiffsleutnant.

Professional officers skipped that rank Fregattenleutnant and were regularly promoted from Seefähnrich to Fregattenleutnant (also OF-1a), the next higher rank (comparable to Oberleutnant zur See).

The rank designation Fregattenleutnent was used continuously in naval forces of former Yugoslavia and as junior officer (OF-1a) rank in modern today's naval forces of Croatia, Slovenia and Serbia.