A waqf, also called a ḥabs, or mortmain property, is an inalienable charitable endowment under Islamic law. It typically involves donating a building, plot of land or other assets for Muslim religious or charitable purposes with no intention of reclaiming the assets. A charitable trust may hold the donated assets. The person making such dedication is known as a waqif ('donor') who uses a mutawalli ('trustee') to manage the property in exchange for a share of the revenues it generates. In Ottoman Turkish law, and later under the British Mandate of Palestine, a waqf was defined as usufruct state land from which the state revenues are assured to pious foundations. It allows the state to provide social services in accordance with Islamic law while contributing to the preservation of cultural and historical sites. Although the waqf system depended on several hadiths and presented elements similar to practices from pre-Islamic cultures, it seems that the specific full-fledged Islamic legal form of endowment called waqf dates from the 9th century AD.

A financial endowment is a legal structure for managing, and in many cases indefinitely perpetuating, a pool of financial, real estate, or other investments for a specific purpose according to the will of its founders and donors. Endowments are often structured so that the inflation-adjusted principal or "corpus" value is kept intact, while a portion of the fund can be spent each year, utilizing a prudent spending policy.