What rank is represented by O-6 in the Navy?

The rank represented by O-6 in the Navy is Captain. In military rank structures, commissioned officer ranks are denoted by letter designations, and "O" refers to officer ranks. Specifically, O-6 corresponds to the rank of Captain in the Navy, making it a senior officer rank just below Admiral. This rank involves significant responsibilities, including overseeing large naval operations or commands.

The other ranks listed do not correlate with the O-6 designation. For instance, Chief Petty Officer and Senior Chief Petty Officer are enlisted ranks, while Rear Admiral is a flag officer rank, which falls into the O-7 category. Therefore, the only rank corresponding to O-6 is indeed Captain.