Romulan ranks

The Romulan military ranks were descended from the ancient Vulcan ranking system which was also used by the Vulcan military until the mid-22nd century. It bore some resemblance to various Earth ranking systems. The Tal Shiar used a different ranking system, although they were used interchangeably with the Guard ranks.

General
General was more of a political position than a rank. 
 * General Movar
 * General Velal

Admiral
Admiral was a flag officer rank in the Guard. Some ex-senators held this rank. 
 * Admiral Alidar Jarok
 * Admiral Mendak
 * Admiral Valdore

Commander
Commander was equivalent to a Starfleet captain. 
 * Commander Donatra
 * Commander Konsab
 * Commander Sela
 * Commander Tomalak
 * Commander Toreth

Subcommander
The rank of subcommander was immediately below that of a commander. 
 * Subcommander N'Vek
 * Subcommander Sela
 * Subcommander Selok
 * Subcommander Tal
 * Subcommander T'Rul
 * Subcommander Velal

Centurion
Centurion was a rank equal to that of lieutenant commander. 
 * Centurion Bochra

Sublieutenant
Sublieutenant was one of the junior ranks in the Guard. 
 * Sublieutenant Setal

Uhlan
An uhlan was described as a "lowly" member of the Guard. 
 * Uhlan Neral

Colonel
Colonel was a rank reserved for senior members of the Tal Shiar. A colonel could command a fleet of Tal Shiar starships. 
 * Colonel Lovok

Major
Major was a lower rank in the Tal Shiar. A member of the Tal Shiar for only several months could gain this rank. 
 * Major Rakal

Background information
Given the rank of sublieutenant, there is presumably a lieutenant rank at some point in the Romulan military history. No Romulan has been referred to as a "Lieutenant" in Trek.

The script for refers to a "Romulan Captain," although this is not used on-screen. The existence of a captain rank is seemingly discredited by Ensign Stefan DeSeve in.

The ranks of centurion and uhlan are ancient Earth ranks (Roman and Polish respectively) not known to be used by any other Star Trek cultures. The reason for their use in the Romulan language or by the universal translator is unknown.

Romulanerränge Rangos Romulanos Grades romuliens ロミュラン軍の階級 Romulan rangen