Lieutenant commander (LCDR) is a junior officer rank in the United States Navy, the United States Coast Guard, the United States Public Health Service Commissioned Corps, and the National Oceanic and Atmospheric Administration Commissioned Officer Corps (NOAA Corps), with the pay grade of O-4 and NATO rank code OF-3.

[1] This can be seen by lieutenant commanders not wearing the headgear embellishment (colloquially known as "scrambled eggs") on their combination covers.

[citation needed] The U.S. Coast Guard used its own rank system until World War I.

In 1916, discontent grew among Coast Guard captains:[2] By law, they ranked below a lieutenant commander in the U.S. Navy despite similar roles and duties.

Pursuant to the Appropriations Act of 1918, the Coast Guard adopted the U.S. Navy rank structure to prevent disagreements over seniority.