Halos, Greek sanctuary near Temple of Apollo in Delphi, Greece.

The Halos is a round open space in the sanctuary of Apollo at Delphi, set between the Bouleuterion and the Sibyl's Rock at the head of a narrow pass leading to the fountain guarded by Python. Its name means threshing floor. To the northeast it is bounded by the Polygonal wall, built after 548 BC to support the ground for the new temple, and on its north side stood the Portico of the Athenians.

The Halos takes its name from the Greek word for a threshing floor, a round open space formed in front of the rocks marking the pass between the Bouleuterion and Sibyl's Rock. Its northeast edge is bounded by the Polygonal wall, built after the Temple of Apollo burned in 548 BC to support the ground for the Alcmaeonids' new temple. In the Hellenistic period platforms and monument bases were set up around it, including the base for a statue of the Pergamene king Attalus II Philadelphus (159–138 BC), dedicated by Delphi. In 1939, during repairs along the Sacred Way, a repository of burnt ex-votos was found in front of the Halos, among them chryselephantine statues of Apollo and Artemis and a silver bull.

The name Halos means "threshing floor", a round open space where the Septerion was held every eight years: a boy with both parents living burned a wooden structure representing Python's dwelling, then cleansed himself as Apollo had done at Tempi. Plutarch describes the rite.

This site is accessible through the main entrance of the Delphi archaeological site and can be visited year-round. It is advisable to arrive in early morning hours to view the structures in better light and avoid large visitor groups.

In 1939, repairs along the Sacred Way uncovered a bothros in front of the Halos filled with burnt votive offerings, buried because it was forbidden to recycle or sell them. Among them were chryselephantine statues of Apollo and Artemis and a silver bull.