Centauri Houses are the Republic's chief societal unit and is formed from old families of varying power, wealth and influence. The Noble Houses are the "Old Guard" while the so-called Great Houses serve as a middle class, though many of the Centaurum and the Republic's other leaders come from such houses. The Lesser Houses make up the lower servant and working classes. Most Centauri are allied to one House or another, either by way of blood relation, arranged marriages or in service as retainers. The few families that have no such alliances - known as Houseless families - are considered beneath contempt.
- House Cotto: Once a relatively minor player among the Great Houses, House Cotto would eventually rise to power, rather surprisingly from Vir Cotto's close association with Londo Mollari.
- House Davo: House Davo's position in the royal court had been purchased from House Miro some time prior to August 2262.
- House Dei: By 2262 House Dei had become a fallen house, bereft of power and money. Shiri Dei was a member of this house.
- House Drusella: During the Second Centauri Occupation of Narn, Lord Drusella was put in charge of the genetic cleansing programs devised by Lord Refa. Drusella even allowed his daughter to assist him with the exterminations.
- House Jaddo: House Jaddo was a respected Centauri house that fell victim to the machinations of Lord Antono Refa and ceased to exist in 2259 when the death of Urza Jaddo at the hands of Londo Mollari allowed the surviving members of House Jaddo to be honourably taken in by their long time ally, House Mollari.
- House Kiro: An ancient and distinguished house that fell into disfavour after it was held responsible for the loss of The Eye at the Battle of Nu'Shok. Lord Kiro and the Lady Ladira visited Babylon 5 in 2258 in the hopes of retrieving the lost trinket.
- House Milifa: In 2275 House Milifa was one of the most powerful and influential houses in all the Centaurum. The young Throk Milifa had been one of the first to join the Prime Candidates while Lord Milifa himself foolishly made an enemy of Minister Durla.
- House Miro House Miro was a noble family with an old blood. However, by 2262 it had little in the way of money and their position in the royal court had been sold to House Davo years before. In 2262, Delasi Miro was proclaimed prophetess supreme.
- House Mollari: An old house that boasted two Emperors in its history; Emperor Mollari I and Emperor Londo Mollari. In 2259 House Jaddo and it's surviving members were made a part of House Mollari.
- House Refa: An old house that was one of the most prestigious and powerful while it was headed by Lord Antono Refa. They fell into disgrace after the death of Lord Refa on the Narn homeworld that brought to light evidence that he had been colluding with the Narn to further his ambitions and had even had a hand in the assassination of the late Prime Minister Malachi. In 2262, Antono's widow Celes Refa was killed when their house was destroyed in the Assault on Centauri Prime by Interstellar Alliance forces, leaving their daughter Senna homeless. By chance Senna was taken in by Emperor Londo Mollari as his ward and years later, she married Emperor Vir Cotto.
- House Tavari: House Tavari were an armaments manufacturing House that owned facilities at the Hevaria Orbital Shipyards over Tolonius VII. They were responsible for the manufacture of Primus class battle cruisers, Vorchan class medium warships and Sentri class fighters.
- House Xarmov: House Xarmov Transports were a major commercial ship manufacturing House that owned facilities at the Hevaria Orbital Shipyards over Tolonius VII. They were responsible for the manufacture of Centauri Atmospheric Shuttles.