Theatre of Thorikos, Ancient theater ruins near Lavrio, Greece

The Theatre of Thorikos is an ancient Greek theatre on the southern slope of Velatoúri hill, in the Lavreotiki area of southern Attica, Greece. The stone seating rows run in an elongated, almost oval shape and face southwest, with vertical staircases dividing the tiers.

The Theatre of Thorikos was built in several phases, the first dating to the end of the Archaic period, with the main structure erected around 525–480 BC. It is the oldest known theatre in the world. Its layout departs from the usual semicircular Greek plan, taking an elongated form instead.

The theatre lies in the mining district of Laurion, and its name comes from Thorikos, the ancient deme of Attica where it stands. The site is associated with the earliest phase of Greek theatre, and visitors can still see the elongated seating cut into the hillside.

The site is on a hillside, so sturdy shoes are a good idea as the ground is uneven and the stone rows are not easy to move around on. There is little shade on the site, so visiting in the early morning or late afternoon is more comfortable.

The theatre's elongated shape does not match any standard Greek theatre plan, which puzzled Belgian archaeologists who have been excavating the site since the 1960s. Some researchers believe the natural contour of the hill forced the builders to abandon the usual semicircular model from the very start.