The Epistles (or Letters) of Horace were published in two books, in 20 BC and 14 BC, respectively.
- Epistularum liber primus (First Book of Letters) is the seventh work by Horace, published in the year 20 BC. This book consists of 20 Epistles. The phrase sapere aude ("dare to be wise") comes from this collection of poems.
- Epistularum liber secundus (Second Book of Letters) was published in the year 14 BC. This book consists of 3 Epistles. However, the third epistle – the Ars Poetica – is usually treated as a separate composition.