Gaius Julius Caesar Octavianus (later known as Augustus Caesar) was the great-nephew and adopted son and heir of Julius Caesar. After the assassination of Julius Caesar, Augustus Caesar formed the Second Triumvirate along with Mark Antony and Marcus Aemilius Lepidus. Togther they hunted down the assassinators of Julius Caesar and also oversaw the outlawing of 300 Roman senators.
After the Triumvirate's term expired in 33 BCE, Augustus Caesar and Mark Antony began to turn on each other. Although Antony was married to Augustus' sister, he lived openly in Alexandria with Cleopatra. Augustus Caesar worked to turn Roman public opinion against Antony, and after he obtained a copy of Antony's will that promised substantial lands to his children with Cleopatra, was able to convince the Roman Senate to revoke Antony's powers and declare war.
After the defeat of Antony and Cleopatra and the end of the civil war, Augustus Caeser worked to covertly consolidate power. On January 16, 27 BCE the Senate gave him the new titles of Augustus and Princeps, effectively marking the end of the Roman Republic and the begining of the Roman Empire.