The Lyran Commonwealth (also known as the Federated Commonwealth or the Lyran Alliance) is one of the major Successor State of the Inner Sphere, located in the coreward, anti-spinward region of space relative to Terra, and traditionally regarded as the wealthiest. For the majority of its history, the Lyran capital was located at the Triad on the icy world of Tharkad. While the Commonwealth was the realm of House Steiner, the Lyran Alliance was ruled by the Steiner-Davion family.

The Lyran Commonwealth is renowned for its strong economy, powerful nobility, and its military policy of promotion based on pedigree as well as talent. Unfortunately for the Lyran state, the promotion of so-called "Social Generals" has resulted in a military of varied capabilities. Even though incompetent "social generals" are not the rule, the prevalence of many poor officers has hindered the Lyran state throughout its history. Additionally, the Lyran Commonwealth Armed Forces tend to fight defensive campaigns with heavier BattleMechs.

Though the military history of the Commonwealth is filled with missteps, the Lyran state has endured for many hundreds of years based on the capabilities of its industrial base and by the merits of the rare, capable officers produced by the system.