The Homeric Hymn to Apollo is the third and one of the longest of the collection, and it falls into two clearly distinct parts: a Delian section on the birth of Apollo on the floating island of Delos, and a Pythian section on his founding of the oracle at Delphi, including his slaying of the she-dragon there. Whether these were ever a single poem is an old and unresolved question in classical scholarship; the two halves differ in geography, emphasis and perhaps date, and many editors treat them as originally separate hymns joined in transmission.
The hymn is also one of antiquity's most quoted self-portraits of the oral poet. In the Delian section the singer addresses the girls who form the chorus at Apollo's festival and asks them, if anyone should come and ask who is the sweetest of singers, to answer that he is a blind man who lives in rocky Chios, a passage ancient readers took as the signature of Homer himself, and modern readers take as a precious, if conventional, glimpse of how such poetry presented its own performance. The ascription to Homer is ancient and, like the rest of the collection, not accepted.
The historian Thucydides quotes several lines of the Delian section in the fifth century BCE as evidence for the ancient Ionian festival at Delos, which makes the hymn one of the few in the collection with an external, datable citation confirming its antiquity by the Classical period. Callimachus and other Hellenistic poets drew on its Delphic material, and the hymn's account of Apollo's birth and his choice of Delphi shaped how later Greek literature imagined the god's two great cult centers.