Sempronius Densus was a centurion in the Praetorian Guard in the 1st century. He was bodyguard to the deputy emperor, and is remembered by history for his courage and loyalty in singlehandedly defending his charge from scores of armed assassins, while all his comrades deserted or switched sides. On January 10, 69, the emperor Galba chose a man to become his deputy and heir. One of Galba's advisors had led Marcus Otho to expect to be appointed to this office, but instead Galba chose one Piso Licinianus. This unexpected choice led Otho to conspire to assassinate both of them and seize power.