Romulan ranks
The Romulan ranking system was a hierarchical collective command structure used within the Romulan Star Empire, seemingly descended from the ancient Vulcan ranking system which was also used by the Vulcan military forces until the mid-22nd century. Both the Tal Shiar and Romulan military had shared but separate ranking system, and their rank insignia shared many of the same physical elements, and appeared in the colors of silver, bronze, and gold.

In 2266, after the commander of the Praetor's flagship learned that one of his officers, Decius, had transmitted a coded message back to Romulus, the commander informed his officer that he was "reduced two steps in rank" on account of "your carelessness might have ended this glorious mission." Following the interaction, the commander's centurion advisor warned that Decius "has friends, and friends of his kind mean power. And power is danger." ()

Military and Tal Shiar

General

A general was a flag officer rank reserved for senior members of both the military and Tal Shiar. During the 2360s and 2370s, their place in the hierarchy was unclear, as one answered to a commander, while another was promoted to general from subcommander. (; ) 

By the 2390s, the rank reserved for senior members of the Tal Shiar. A general could command a fleet of Tal Shiar starships. ()

 General Movar
 General Oh (Tal Shiar)
 General Velal
 Sela's father

Admiral
An admiral was a flag officer rank and position known to be held by field commanders and ex-senators serving in the military. (; )
 Admiral Alidar Jarok
 Admiral Mendak
 Admiral Valdore

Commander

A commander was equivalent to a Starfleet captain. ()

 Commander Donatra
 Commander Konsab
 Commander Rekar
 Commander Sela
 Commander Sirol
 Commander Surak
 Commander Tebok
 Commander Tomalak
 Commander Toreth

Sub-commander

A sub-commander was shared by military and Tal Shiar alike, it was immediately below the rank of a commander. (; , et al.; )

Sub-Commander Almak (Tal Shiar)
Sub-Commander N'Vek
Sub-Commander Selok
Sub-Commander 
Sub-Commander Taris
Sub-Commander Thei
Sub-Commander T'Rul
Sub-Commander Ustard
Sub-Commander Velal

Colonel

A colonel was a rank reserved for senior members of the Tal Shiar. A colonel could command a fleet of Tal Shiar starships. ()

Colonel Lovok
Colonel Narissa

Centurion
A centurion was a general officer's rank. (; )

While posing as a centurion during his attempting to infiltrate Tal's flagship in 2268, Captain James T. Kirk commended a  guard on his alertness, and offered, "I shall remember to mention your alertness to [the sub-commander]," before instructing the guard to "[r]eturn to your duty." ()

Centurion Bochra
Centurion Tarent
Centurion 1 (Praetor's flagship)
Centurion 2 (Tal's flagship)

Major

A major was a rank in the Tal Shiar that may be held by an intelligence officer. A commander will answer to a major, as long as they were not pushed too hard. According to Deanna Troi, who was disguised as a Tal Shiar major, she stated that she had only been an intelligence officer for several months. ()
Major

Sublieutenant
A sublieutenant was a low ranking military rank. Positions known to be held by this rank include logistics officers. ()
Sublieutenant Setal

Uhlan
An uhlan was, perhaps, the lowest ranking member of the Romulan Guard. 

The Romulan Proconsul claimed, in 2368, that he had never liked titles, ever since he had been a "lowly uhlan". ()
Uhlan Neral

Civilian

Captain 
Though not part of the Romulan rank hierarchy, the title  has been used in the Empire, but not in terms of rank. Doctor Telek R'Mor, a low ranking scientist and minor functionary from the Romulan Astrophysical Academy, initially referred to himself as "captain of the cargo vessel Talvath." ()

Political titles 
 Praetor
 Consuls
 Proconsul
 Vice-proconsul
 First consul
 Senator
 Chairman
 Vice-chairman
 Prod

Appendices

See also 
 Romulan rank insignia

Background information 
The ranks of  and  are ancient Earth ranks (Roman and Polish respectively) not known to be used by any other Star Trek cultures. 

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 Star Trek.

In , Ayel refers to Nero as "Prod Nero." In a deleted scene in which the Narada is surround by Klingon warbirds, the subtitles created by the filmmakers for the Romulan dialogue translate Prod as "commander." However, according to a DVD audio commentary for the film, "Prod" was intended to mean "Praetor."

     
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