Agrippa, Marcus Vipsanius (63–12 B.C.), a Roman general and statesman. He was of humble birth but became the leading general, chief adviser, and son-in-law of Octavian, who became the emperor Augustus. Agrippa won the decisive battle of Actium (31), between Octavian and Mark Antony, for Octavian. During the rest of his life he acted as deputy to the emperor. An able organizer and engineer, Agrippa built aqueducts and the original Pantheon. He prepared a map of the world. His third wife was Octavian's daughter Julia.