What is the title for an O-3 rank in the Marine Corps?

In the Marine Corps, the rank of O-3 is designated as Captain. This rank is part of the officer rank structure, where O-1 represents Second Lieutenant, O-2 represents First Lieutenant, and O-3 corresponds to Captain. Captains play a crucial role in leadership and management within military units, typically commanding a company-sized element or serving in various staff positions.

The other ranks mentioned are higher in the structure: Major is an O-4 rank, Lieutenant Colonel is an O-5 rank, and Colonel is an O-6 rank. Understanding the officer rank structure is essential for anyone studying military organization, as it impacts command relationships and responsibilities within the armed forces.