The Coliseum is an elliptical amphitheatre in the centre of the city of Rome, Italy, the largest ever built in the Roman Empire. It is considered one of the greatest works of Roman architecture and Roman engineering.

Occupying a site just east of the Roman Forum, its construction started in 72 AD under the emperor Vespasian and was completed in 80 AD under Titus, with further modifications being made during Domitian's reign (81–96). The name "Amphitheatrum Flavium" derives from both Vespasian's and Titus's family name (Flavius, from the gens Flavia).

Capable of seating 50,000 spectators, the Colosseum was used for gladiatorial contests and public spectacles such as mock sea battles, animal hunts, executions, re-enactments of famous battles, and dramas based on Classical mythology. The building ceased to be used for entertainment in the early medieval era. It was later reused for such purposes as housing, workshops, quarters for a religious order, a fortress, a quarry, and a Christian shrine.

Although in the 21st century it stays partially ruined because of damage caused by devastating earthquakes and stone-robbers, the Colosseum is an iconic symbol of Imperial Rome. It is one of Rome's most popular tourist attractions and still has close connections with the Roman Catholic Church, as each Good Friday the Pope leads a torchlit "Way of the Cross" procession that starts in the area around the Colosseum.

The Colosseum is also depicted on the Italian version of the five-cent euro coin.