The Emperor Nero (Nero Claudius Caesar Augustus Germanicus) was born December 15th, 37 A.D. to Gnaeus Domitius Ahenobarbus, first cousin of the Emperor Claudius, and Agrippina Minor, sister of the Emperor Caligula. Nero was later adopted by his uncle, the Emperor Claudius, and succeeded him in 54 A.D. He was the fifth and final ruler of the Julio-Claudian Dynasty.
The light beard and part above the right eye suggest that this portrait was commissioned late in Nero's life. For more on Nero's portrait types see p. 135-139 in Kleiner, Roman Sculpture.