What is the next highest rank after an O-6?

The next highest rank after an O-6, which is the rank of Captain in the Navy, is Rear Admiral Upper Half. In the U.S. Navy, officer ranks are classified into various tiers, where O-6 specifically denotes the rank of Captain. Progressing up the rank structure, the immediate next step is O-7, which is recognized as Rear Admiral Lower Half, and further advancement leads to O-8, or Rear Admiral Upper Half.

Rear Admiral Upper Half signifies a higher level of leadership and responsibility, often overseeing significant operations and fleets. This rank serves as a crucial stepping stone towards higher flag officer ranks, which include Vice Admiral (O-9) and Admiral (O-10). Understanding this hierarchy is essential for grasping the progression of ranks and the corresponding responsibilities at each level in naval operations.