Hay-on-Wye, often abbreviated to just "Hay", is a small market town and community in the historic county of Brecknockshire in Wales, currently administered as part of the unitary authority of Powys. With over twenty bookshops, it is often described as "the town of books", and is both the National Book Town of Wales and the site of the annual Hay Literary Festival.
The settlement's name is first referred to between 1135 and 1147 as "Haya"; in 1299 the name of "La Haye" is used. By the 16th century it was simply called "Hay", and the use of the river as a suffix is a later addition. In 1215, a Welsh name, "Gelli" was recorded, and "Gelli gandrell" in 1614; the two names may have been used concurrently in 1625. The English language name, "Hay", is derived from Old English "hæg", possibly meaning a "fenced area" and a noun used in late Saxon and Norman times for an enclosure in a forest. The Welsh word celli has a range of meanings including wooded areas of various extents.