Genesius (Greek: Γενἐσιος, Genesios) is the conventional name given to the anonymous Greek author of the tenth century chronicle, On the reign of the emperors. His first name is sometimes given as Joseph, combining him with a "Joseph Genesius" quoted in the preamble to John Skylitzes. Traditionally, he has been regarded as the son or grandson of Constantine Maniakes.
The chronicle describes the reigns of the four emperors from Leo V down to Michael III in detail; and more briefly that of Basil I. It uses Constantine VII's Life of Basil as a source, though it appears to have been finished before Theophanes Continuatus, and gives information present in neither Continuatus nor Skylitzes.