Which event is commonly linked to the beginning of the Roman Empire?

The event commonly linked to the beginning of the Roman Empire is the accession of Augustus as the first emperor. This pivotal moment marked a significant shift in governance from the Roman Republic, characterized by a complex system of elected officials and shared power, to a centralized autocratic form of rule under an emperor.

Augustus, originally known as Octavian, came to power after a period of civil war and political turmoil that followed the assassination of Julius Caesar. His rise initiated a new era in Roman history, known as the Empire, which would drastically alter the political landscape and lead to a period of relative peace and stability known as the Pax Romana. This transformation established the foundation for imperial administration, identity, and expansion that characterized Rome during the following centuries.

In contrast to this moment, while the founding of Rome and the establishment of the Senate are significant in their own rights, they pertain to earlier phases of Roman history. The construction of the Colosseum represents an achievement of the empire but occurs later and does not signify its foundational moment. Thus, the crowning of Augustus as the first emperor is the definitive event that marks the beginning of the Roman Empire.