In most Inner Sphere and Periphery militaries, soldiers with the rank of Captain command companies. In the various naval forces, the rank of Captain is usually a ship's commanding officer and is roughly equivalent to a Colonel of ground forces.
In the first Star League, a Captain commanded a company of ground forces. In the SLDF Navy, they commanded DropShips. In any case, these officers were expected to demonstrate initiative.
In the second Star League a Captain is the front line commander of a company of ground troops. Unlike their first Star League counterparts, SLDF Navy officers at this rank are called Commander and command a flight of AeroSpace Fighters, a DropShip, or act as the Executive Officer of a JumpShip or WarShip.
In both cases, the rank insignia for an SLDF Captain is two green bars.
SLDF Rank insignia
|| Insignia (First SLDF)
|| Insignia (Second SLDF)
 Lyran Commonwealth and Lyran Alliance
The LCAF and LAAF use the rank of Hauptmann for company commanders. These officers are the highest rank that routinely see combat. To honor these officers, the Lyran Alliance's first OmniMech was named the Hauptmann.
LAAF Military Rank Insignia
 Draconis Combine Mustered Soldiery
The DCMS uses Tai-i to indicate company commanders. Their symbol is a royal blue "5". The Draconis Combine Admiralty rank is Chu-i. A chu-i in the DCA frequently commands a flight of six AeroSpace Fighters.
 Armed Forces of the Federated Suns
Captains in the AFFS use an epaulette with one narrow band across the base as their rank insignia.
AFFS Captain's Insignia by branch of service.
|| AeroSpace Fighter
|| Naval Crew
|| Logistics/ |
 Capellan Confederation Armed Forces
Prior to Sun-Tzu Liao's ascension to the Celestial Throne, the CCAF used the rank of Captain to indicate the commanding officer of a company. Due to the CCAF's unique rank structure at that time, Captains and Majors were assigned to a variety of different duties that would be handled by higher ranking officers in other militaries.
After Sun-Tzu became Chancellor, he introduced several new ranks into the CCAF as part of Xin Sheng. These ranks were given new Chinese names, and resulted in several promotions. Officers who held the rank of Captain under Romano Liao were renamed Sao-shao equivalent to Major in other militaries. Officers who command companies now hold the rank of Sang-wei. Their rank insignia is a brass bar with a single silver pip. 
The CCAF Admiralty rank uses the same insignia, but is named Kong-sang-wei.
 Free Worlds League
Like their counterparts in other Successor States, FWLM Captains are company commanders. They use two thick gold bars on a purple background as their rank insignia. In the FWLM Navy, an officer at this level is known as a Lieutenant Commander and commands a ship's watch or heads up a department aboard ship.
FWLM Captain's Military Rank Insignia
 The Clans
Star Captain is the rank used by the Clans for the commanding officer of a Binary or Trinary. Commanders of DropShips and JumpShips are also given the rank of Star Captain. Clan Hell's Horses also uses the rank of Nova Captain, who commands a Supernova.
 Clan Blood Spirit
 Clan Cloud Cobra
 Clan Coyote
The Nova Captain rank used by the Coyotes could be considered equal to either a senior Inner Sphere Captain or a Major, depending on the holder's experience.
 Clan Diamond Shark
 Clan Fire Mandrill
 Clan Ghost Bear
 Clan Goliath Scorpion
 Clan Hell's Horses
The Nova Captain rank used by the Horses could be considered equal to either a senior Inner Sphere Captain or a Major, depending on the holder's experience.
 Clan Ice Hellion
 Clan Jade Falcon
 Clan Nova Cat
 Clan Nova Cat (SLDF)
 Clan Sea Fox
 Clan Smoke Jaguar
 Clan Snow Raven
 Clan Star Adder
 Clan Steel Viper
 Clan Wolf / Clan Wolf-in-Exile
 Comstar/Word of Blake
The ComGuard and Word of Blake Militia don't use this rank. Instead their Level II formations are led by an Adept.
 Free Rasalhague Republic
In the KungsArmé officers with this rank are called Kapten, Swedish for Captain. These soldiers wear a green patch with a vertical silver bar crossed at the base by a small silver bar as their rank insignia.
KungsArmé Military Rank Insignia
 Periphery Powers
 Magistracy of Canopus
In the Magistracy Armed Forces, purchasing a company command means the officer holds the rank of Commander. This rank is also used by the Magistracy Navy. Commanders wear two gold edged blue-green diamonds set inside each other to show their rank.
 Taurian Defense Force
In the TDF, company commanders use the rank of Subaltern. This should not be confused with the AFFS rank. The Taurian Defense Force Navy uses Air Master, Junior Grade or Air Master, JG for officers at this rank. In either case, their rank insignia is a single gold ring filled with a red dot.
 Marian Hegemony
With the interest the Legiones Marianes have in recreating the Roman Empire, company commanders are known as Principes, a Latin word meaning leader or ruler. (To avoid annoying the Imperator and Caesar, the latter translation isn't used.) A principes wears the silver triangle of a legionnaire with an inset black triangle to show their rank.
 Outworlds Alliance
In the Alliance Military Corps, company commanders are known as Section Leaders. Their rank insignia is a pair of vertically stacked Supervisor's green bars.
- ↑ The Star League, p. 112
- ↑ Field Manual: ComStar, p. 80
- ↑ The Star League, p. 113
- ↑ Field Manual: ComStar
- ↑ House Kurita (The Draconis Combine), p. 129
- ↑ Field Manual: Draconis Combine, p. 19
- ↑ House Davion (The Federated Suns), p. 126
- ↑ Field Manual: Capellan Confederation
- ↑ Field Manual: Free Worlds League, p. 22
- ↑ Field Manual: Warden Clans, p. 48
- ↑ Field Manual: Crusader Clans, p. 45
- ↑ Field Manual: Crusader Clans, p. 97
- ↑ Field Manual: ComStar, p. 112
- ↑ Field Manual: Warden Clans, p. 127
- ↑ Field Manual: Crusader Clans, p. 120
- ↑ Field Manual: ComStar, p. 66
- ↑ Field Manual: Periphery, p. 24
- ↑ Field Manual: Periphery, p. 53
- ↑ Field Manual: Periphery, p. 73
- ↑ Field Manual: Periphery, p. 88