Captain is a rank in branches of the military. The rank varies in importance amongst different branches of service. In the Navy, it de facto implies the right to command a ship, especially in popular culture, as well as implying an elevated grade of other responsibility. However, often lieutenant commanders enjoy the right of command.
In general, the rank comes after a lieutenant post, and before a major post. In the British Royal Navy, the rank of "Captain" was a formalistic term, which meant only the honorific of command. An officer may be a "Captain" while still a lieutenant, but was not a formal rank. "Post-Captain" was the actual rank carrying the term. This distinction is obsolete.
- For artistic illustration, see Patrick O'Brian's novel Post Captain.