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.