Which rank is denoted by O-1?

The rank denoted by O-1 in the Navy is an Ensign. This is the entry-level rank for officers in the Navy and is the first step in the officer rank structure. Officers at this rank typically have responsibilities that include leading junior personnel, making decisions related to their assigned tasks, and engaging in training and development opportunities to advance their careers.

In the context of the Navy's rank system, enlisted personnel hold ranks that fall below the officer ranks. Chief Petty Officer, Master Chief Petty Officer, and Senior Chief Petty Officer are all ranks that belong to the enlisted category, which does not include any officer ranks. Therefore, they cannot be classified as O-1 ranks. Understanding the distinction between officer and enlisted ranks is crucial when studying military structure and promotions.