Nerva Marcus Cocceius (about 32–98 A.D.), a Roman emperor. Nerva, who had served as a consul under emperors Vespasian and Domitian, was proclaimed emperor by the Roman Senate in 96 after the assassination of Domitian, who had no heir. He was the first of the "Five Good Emperors," who ruled during 96–180.
As emperor, Nerva introduced a program of tax, land, and financial reforms. His reign was just and enlightened. He was, however, unable to control the Praetorian Guard, whose leadership was angered by his refusal to surrender Domitian's assassins to them. When the Guard threatened revolt in 97, Nerva, who was ill and had no son, adopted Trajan, a popular general, as his heir and gave him full powers. He thus initiated the practice of adoptive succession, which replaced hereditary succession until 180.