William Barley (1565?–1614) was an English bookseller and publisher. He completed an apprenticeship as a draper in 1587, but was soon working in the London book trade. As a freeman of the Drapers' Company, he was embroiled in a dispute between it and the Stationers' Company over the rights of drapers to function as publishers and booksellers. He found himself in legal tangles throughout his life.
Barley's role in Elizabethan music publishing has proved to be a contentious issue among scholars. The assessments of him range from "a man of energy, determination, and ambition", to "somewhat remarkable", to "surely to some extent a rather nefarious figure". His contemporaries harshly criticized the quality of two of the first works of music that he published, but he was also influential in his field.
Barley became the assignee of Thomas Morley, who as well as being a composer held a printing patent (a monopoly of music publishing). He published Anthony Holborne's Pavans, Galliards, Almains (1599), the first work of music for instruments rather than voices to be printed in England. His partnership with Morley enabled him to claim rights to music books, but was short-lived. Morley gave work to the printer Thomas East, and died in 1602. Some publishers ignored Barley's claims, and many music books printed during his later life gave him no recognition.
In a deposition of 1598, Barley refers to his age as "xxxiii yeeres or thereabowt", placing his date of birth around 1565. Evidence suggests that Barley may have been born in Warwickshire. Little else is known about his early life. Barley was in London by 1587, having completed an apprenticeship with the Drapers' Company in that year. He trained as a bookseller under Yarath James, a small-time publisher. James operated out of a shop in Newgate Market, near Christ Church Gate, in the 1580s. His interest in ballads was shared by Barley, who published a number of them during his lifetime. By 1592, Barley had opened his own shop in the parish of St Peter upon Cornhill, whose register recorded his marriage to a Mary Harper on 15 June 1603 and christenings and burials of people associated with his family. He conducted business out of this shop for the next twenty years.