Lieutenant commander (often abbreviated Lt Cdr), formerly more commonly lieutenant-commander, is a senior officer rank in the Royal Navy of the United Kingdom.

[citation needed] The insignia worn by a Royal Navy lieutenant commander is two half-inch gold braid stripes with one quarter-inch gold stripe running in between, placed upon a navy blue background.

The RAF follows this pattern with its equivalent rank of squadron leader.

The ROC wore a Royal Air Force uniform and their rank insignia appeared similar to that of an RAF squadron leader except that the stripes were shown entirely in black.

Prior to the renaming, the rank had been known as observer lieutenant (first class).