Marcus Annius Flavius Libo was a Roman politician and Senator at the beginning of the 3rd century and a member of the Antonine Dynasty.
Libo was a Patrician and came from Hispania Baetica.
His grandfather was Marcus Annius Libo who was made suffect consul in 161 AD. His father was a legatus of Syria and was poisoned possibly by his cousin the Emperor Marcus Aurelius. Libo became ordinary Consul in 204. He was related to Marcus Aurelius through their mutual ancestor Marcus Annius Verus who was consul three times; and by marriage to Antonius Pius who married his grandfather's sister.