O-5 in the Marine Corps is the rank of?

The rank of O-5 in the Marine Corps is Lieutenant Colonel. In the military ranking system, officer ranks are denoted by a letter and a number; the letter "O" refers to officer ranks, and the number indicates the level of the rank. For O-5, this corresponds specifically to the rank of Lieutenant Colonel, which typically involves responsibilities such as commanding a battalion or serving in senior staff roles, often necessitating significant leadership and operational experience.

In contrast, Major, which is O-4, comes before Lieutenant Colonel, while Colonel, represented as O-6, follows it. Captain is considered O-3, which is a step below Major. Understanding these distinctions is crucial for recognizing the hierarchy within the Marine Corps and other branches of the military.