In Classical Antiquity, an oracle was a person or agency considered to interface wise counsel or prophetic predictions or precognition of the future, inspired by the gods. As such it is a form of divination.

The word oracle comes from the Latin verb ōrāre "to speak" and properly refers to the priest or priestess uttering the prediction. In extended use, oracle may also refer to the site of the oracle, and to the oracular utterances themselves, called khrēsmoi in Greek.

Oracles were thought to be portals through which the gods spoke directly to people. In this sense they were different from seers who interpreted signs sent by the gods through bird signs, animal entrails, and other various methods.

The most important oracles of Greek antiquity were Pythia, priestess to Apollo at Delphi, and the oracle of Dione and Zeus at Dodona in Epirus. Other temples of Apollo were located at Didyma on the coast of Asia Minor, at Corinth and Bassae in the Peloponnese, and at the islands of Delos and Aegina in the Aegean Sea. The Sibylline Oracles are a collection of oracular utterances written in Greek hexameters ascribed to the Sibyls, prophetesses who uttered divine revelations in a frenzied state.