Creatio ex nihilo (Latin, 'creation out of nothing') or nihilogony is the doctrine that matter is not eternal but had to be created by some divine creative act. It is a theistic answer to the question of how the universe came to exist. It is in contrast to Creatio ex materia resultante ex aseitate logica (creation from matter resulting from logical aseity; but modern foundationalism is cosmological with improvements from the 17th century viewpoint), sometimes framed in terms of the dictum ex nihilo nihil fit or 'nothing comes from nothing', meaning all things were formed ex materia (that is, from pre-existing things).

Creatio ex materia refers to the idea that matter has always existed and that the modern cosmos is a reformation of pre-existing, primordial matter; it is sometimes articulated by the philosophical dictum that nothing can come from nothing.

In ancient Near Eastern cosmology, the universe is formed ex materia from eternal formless matter, namely the dark and still primordial ocean of chaos. In Sumerian myth this cosmic ocean is personified as the goddess Nammu "who gave birth to heaven and earth" and had existed forever; in the Babylonian creation epic Enuma Elish, pre-existent chaos is made up of fresh-water Apsu and salt-water Tiamat, and from Tiamat the god Marduk created Heaven and Earth; in Egyptian creation myths a pre-existent watery chaos personified as the god Nun and associated with darkness, gave birth to the primeval hill (or in some versions a primeval lotus flower, or in others a celestial cow); and in Greek traditions the ultimate origin of the universe, depending on the source, is sometimes Oceanus (a river that circles the Earth), Night, or water.

Similarly, the Genesis creation narrative opens with the Hebrew phrase bereshit bara elohim et hashamayim ve'et ha'aretz, which can be interpreted in at least three ways:

Though option 1 has been the historic and predominant view, it has been suggested since the Middle Ages that it cannot be the preferred translation based on strictly linguistic and exegetical grounds. Whereas our modern societies see the origin of matter as a question of crucial importance, this may not have been the case for ancient cultures. Some scholars assert that when the author(s) of Genesis wrote the creation account, they were more concerned with God bringing the cosmos into operation by assigning roles and functions.

Creatio ex nihilo is the doctrine that all matter was created out of nothing by God in an initializing act whereby the cosmos came into existence. The third-century founder of Neoplatonism, Plotinus, argued that the cosmos was instead an emanation of God. Emanationism was rejected by Jewish philosophers, as well as the Church Fathers and Muslim philosophers who followed.

African traditional religions tend to favour creatio ex materia over creatio ex nihilo, and it is absent in Akan, Acholi, and Yoruba religions. Ghanaian philosopher Kwasi Wiredu has argued that some religions such as those of the Shona, Nuer, and Banyarwanda "affirm the notion of creatio ex nihilo".

Although ancient near-eastern cosmology is read as invoking a process of creatio ex materia, occasional suggestions have been made that creatio ex nihilo can be found at least in some texts, including the Egyptian Memphite theology and the Hebrew Biblical Genesis creation narrative. Hilber rejected these interpretations, viewing both as consistent with creatio ex materia and instead suggesting that some passages in the Book of Isaiah, the Book of Proverbs, and the Psalms indicate a form of creatio ex nihilo. The cosmogonical doxologies of the Book of Amos also present a view of creation ex nihilo.