Usury (pronounced /ˈjuːʒəri/, comes from the Medieval Latin usuria, "interest" or "excessive interest", from the Latin usura "interest") originally meant the charging of interest on loans. This would have included charging a fee for the use of money, such as at a bureau de change. After countries legislated to limit the rate of interest on loans, usury came to mean the interest above the lawful rate. In common usage today, the word means the charging of unreasonable or relatively high rates of interest. As such, the term is largely derived from Abrahamic religious principles; Riba is the corresponding Islamic term. The primary focus in this article is on the Christian tradition.

The pivotal change in the English-speaking world seems to have come with the permission to charge interest on lent money: particularly the Act 'In restraint of usury' of Henry VIII in England in 1545 (see book references).