Final answer:
Octavian ended a period of civil war in Rome, and the Senate granted him the title Augustus in 27 BCE, marking the establishment of the Roman Empire and his rule as its first emperor.
Step-by-step explanation:
The Roman emperor who was named Augustus after ending a civil war was Octavian, also known as Gaius Octavius. He triumphed over Mark Antony and Cleopatra, and later the Senate awarded him the title Augustus, meaning "illustrious" or "semi-divine," in 27 BCE. This marked the foundation of the Roman Empire and the end of the Republic. Augustus cleverly positioned himself as the Princeps Civitatus, or "First Citizen," to avoid the connotations associated with kingship, while effectively retaining imperial power. He initiated a period of relative peace and prosperity known as the Pax Romana and reformed various aspects of Roman society, government, and military. Despite having no biological son, he ensured a smooth succession by grooming his stepson, Tiberius, to take over the Empire.