This is the first comprehensive commentary on Callimachus' Hymn to Delos, its immediate predecessor being Cahen's concise work of 1930. The Introduction proposes a new interpretation of the Hymn's purpose and background, and further discusses the date of its composition, its vocabulary, several of its stylistic aspects, and its metre and prosody. The Commentary, which follows Pfeiffer's text (Oxford 1953), presents parallels from relevant Greek poetry (mainly epic and tragic) to illustrate tradition and originality in Callimachus' style, offers some new interpretations and examines old ones, and indicates possible allusions to contemporary events in Egypt and elsewhere. Textual problems are treated where necessary and emendations are also occasionally proposed.