Eobacterium is a fossil genus of probable bacteria from the Fig Tree Formation in South Africa. It lived during the Paleoarchean era, around , making it one of the oldest known organisms if it is valid. The discovery of Eobacterium and other Fig Tree organisms such as Archaeosphaeroides in the 1960s helped prove that life existed over three billion years ago.
The genus is monospecific, and contains one species, Eobacterium isolatum.