Natural theology is a branch of theology based on reason and ordinary experience. Thus it is distinguished from revealed theology which is based on scripture and religious experiences of various kinds; and also from transcendental theology, which is based on a priori reasoning.

Marcus Terentius Varro (116–27 BC) in his (lost) Antiquitates rerum humanarum et divinarum established a distinction between three kinds of theology: civil (political) (theologia civilis), natural (physical) (theologia naturalis) and mythical (theologia mythica). The theologians of civil theology are "the people", asking how the gods relate to daily life and the state (imperial cult). The theologians of natural theology are the philosophers, asking about the nature of the gods, and the theologians of mythical theology are the poets, crafting mythology. The terminology entered Christianity after having been adopted by the Stoic tradition; it is used by St. Augustine and St. Thomas Aquinas.

Natural theology therefore is a branch of philosophy, whose object is the nature of the gods, or of the one supreme God. In monotheistic religions, this principally involves arguments about the attributes or non-attributes of God, and especially the existence of God - arguments which are purely philosophical, and do not involve recourse to any supernatural revelation.

The related term Physico-theology describes a theology based on the constitution of the natural world. This often proceeds by invoking the need for a designer. One of the first examples of this approach to theology was the fifth of St. Thomas Aquinas's "five ways" to prove the existence of God.