The Batarian Hegemony is a minor interstellar power in the Mass Effect universe.
Batarian society is organized along class lines, including a slave caste. Batarians typically regard all non-batarians as members of the slave caste, resulting in constant tension due to batarian slave traders raiding isolated settlements of other species.
The Batarian Hegemony is a significant power in the Mass Effect setting, with military assets capable of threatening the Systems Alliance in a "cold war" over disputed territory. Batarian dreadnoughts are mentioned on several occasions, though no specific number is ever given. The batarians are probably the most powerful of the non-Council races in Mass Effect.
The batarians were the first race hit by the Reaper invasion, which quickly overwhelmed them. By the end of Mass Effect 3, the military and political power of the Batarian Hegemony is drastically reduced in comparison to other Mass Effect races.