The Sacred Way (Ancient Greek: Ἱερὰ Ὁδός, Hierá Hodós), in ancient Greece, was the road from Athens to Eleusis. It was so called because it was the route taken by a procession celebrating the Eleusinian Mysteries. The procession to Eleusis began at the Sacred Gate in the Kerameikos (the Athenian cemetery) on the 19th Boedromion.

In the present day, the road from central Athens to Aegaleo and Chaidari (the old route to Eleusis) is called the Iera Odos after the ancient road.

The sacred rites of Demeter were performed in Eleusis in Ancient Greece beginning as far back as the 15th Century BCE, according to some sources. According to the Homeric Hymns of the Archaic period, Demeter stopped at Eleusis during her quest for Persephone. The story describes how Demeter, persuaded to stay at the palace of Eleusis by its prince, Celeus, was given the task of raising Celeus's son Demophon. When she is discovered to be a Goddess by the queen Metaneira after trying in vain to make Demophon immortal, she instructed the Eleusinians to build a temple for her. Upon later finding Persephone, she taught the leaders of Eleusis how to perform her rites.

Unlike many of the cults in the Ancient Greek world, the cult of Demeter kept its rites a secret except for a chosen few, thus warranting the name the Eleusinian Mysteries. While at first the cult of Demeter remained small, it eventually grew quite large after Eleusis was incorporated into Athens during the Archaic period. After some time, it drew crowds from thousands of people around Greece, and even leaders like Peisistratos, Pericles, Hadrian, and Antoninus Pius all came to erect monuments at Eleusis. In addition, the rites became so important to the Greeks that until Roman rule, the Sacred Way remained the only road in central Greece.

Although the cult of Demeter kept information about its rites a secret only to those in the cult, the cult itself was open to a wide array of people. Initiates could be young or old, male or female, even slave or free. The only requirement, it seems, is that initiates could not have any sort of un-atoned bloodguilt on their hands.

The process for initiates began six months before the procession along the Sacred Way. The initiation began at the beginning of spring with instruction on the Lesser Mysteries, which mostly celebrated the arrival of spring and allowed for initiates to atone themselves in preparation for the Greater Mysteries later on in the fall. After these preliminary steps, and one month before the procession in Boedromion, special messengers, called the spondophoroi, were sent out from Eleusis to herald the coming of the procession all around Greece. Finally, on the 13th of Boedromion, priestesses of Demeter and Persephone carried baskets of Sacred Objects, called the hiera, from Eleusis to Athens in preparation for the procession and the rites of the Greater Mysteries.

On the first day of the celebration, initiates dressed in simple attire gathered with their teachers, as well as a large crowd, in the Agora in front of the Stoa Poikile for the proclamation by the hierophant of Demeter. The proclamation welcomed any initiate who was not morally corrupt, instructed initiates to not reveal the experiences of the rites, and told them that they must fast between sunup and sunrise during the celebration. The day then ended with a parade up to the sacred precinct of Demeter called the Eleusinion.

The second day started early with initiates walking with their teachers, families, and friends to submerge themselves in the Bay of Phaleron. This may have been seen as a physical and spiritual cleansing ceremony for the initiates.