A mortgage is a method of using property (real or personal) as security for the payment of a debt.

The term mortgage (from Law French, lit. dead pledge) refers to the legal device used for this purpose, but it is also commonly used to refer to the debt secured by the mortgage, the mortgage loan.

In most jurisdictions mortgages are strongly associated with loans secured on real estate rather than other property (such as ships) and in some cases only land may be mortgaged. Arranging a mortgage is seen as the standard method by which individuals and businesses can purchase residential and commercial real estate without the need to pay the full value immediately. See mortgage loan for residential mortgage lending, and commercial mortgage for lending against commercial property.

In many countries it is normal for home purchases to be funded by a mortgage. In countries where the demand for home ownership is highest, strong domestic markets have developed, notably in Spain, the United Kingdom and the United States.