De Unione Insulae Britannicae (The British Union) is a unique seventeenth-century tract that urged the fusion of the Scottish and English kingdoms into a new British commonwealth with a radically new British identity. It's author, David Hume of Godscroft (1558-c.1630) was a major intellectual figure in Jacobean Scotland and the leading Scottish critic of the anglicizing policies of James VI.

The tract was written in two parts. Published in London in 1605, the first part provides a general outline of the imperative of union. The second consists of political and constitutional proposals whereby such a union might be achieved. Its publication was suppressed and it exists only in manuscript. This is the first translation of the tract.