Centuries: 2nd century BC – 1st century BC – 1st century
Decades: 90s BC 80s BC 70s BC 60s BC 50s BC – 40s BC – 30s BC 20s BC 10s BC 0s BC 0s
Years: 51 BC 50 BC 49 BC 48 BC 47 BC 46 BC 45 BC 44 BC 43 BC 42 BC 41 BC
- February 6 – Julius Caesar defeats army of Pompeian followers at Thapsus.
- November – Caesar leaves for Farther Spain to deal with a fresh outbreak of resistance.
- The Julian calendar is enacted, so in this year there were 445 days to compensate for past errors. The year is known as the Year of Confusion.
- April 20 – Cicero, in Rome, writes to Varro "If our voices are no longer heard in the Senate and in the Forum, let us follow the example of the ancient sages and serve our country through our writings, concentrating on questions of ethics and constitutional law."