freestanding building of round or, more often, oval shape with a central area, the arena, and seats concentrically placed around it. The word is Greek, meaning “theatre with seats on all sides,” but as an architectural form the amphitheatre is of Italic or Etrusco-Campanian origin and reflects the requirements of the specific forms of entertainment that these people cherished—i.e., gladiatorial games and venationes, contests of beasts with one another or of men with beasts. Originally such games took place in the forum, and wooden stands were erected from time to time to accommodate the spectators. The earliest permanent extant amphitheatre is one at Pompeii (c. 80 BC), in which the arena is sunk below the natural level of the surrounding ground. It is built of stone, 445 by 341 feet (136 by 104 metres), and seated approximately 20,000 spectators.

In most of the Roman amphitheatres, an elaborate labyrinth was constructed below the arena. The passages, including the media via for scenery, spaces for elevators and machinery that lifted the animals and stage sets, and rooms for the gladiators, were ingeniously arranged to connect, by means of many trapdoors, with the arena above. Around this arena, and separated from it by a high wall topped by a metal screen, rose the spectator seats. These were divided by passageways running around the amphitheatre into several sections (maeniana). In the lowest section, or podium, the emperor and his retinue had a special box; on the opposite side of the amphitheatre, but still in the podium, the vestal virgins, consuls, praetors, ambassadors, priests, and other distinguished guests were seated; the rest of the first gallery contained senators and those of the equestrian rank. The second gallery was reserved for patricians, the third for plebeians, and the fourth, uppermost gallery for women, who were seated in boxes. An awning (velum, or velarium) was manipulated by sailors to shelter the spectators from the sun. Each of these galleries was divided into wedge-shaped sections (cunei) by radial walks that led to the many exits (vomitoria).

In modern usage the word amphitheatre is sometimes used for a theatre or concert hall whose seats surround the central area, as, for example, the Albert Hall, London, and both the new and the old Madison Square Garden in New York City. It may also refer to a stadium in which athletic competitions are held.

Outdoor amphitheatres, both ancient and relatively recent (e.g., Chicago's Soldier Field), continue to be used for sports events and many other kinds of entertainment, although in the mid-20th century, the structure took the form of a vast roofed stadium.