Creationism is the religious belief that nature, and aspects such as the universe, Earth, life, and humans, originated with supernatural acts of divine creation, and is often pseudoscientific. In its broadest sense, creationism includes various religious views, which differ in their acceptance or rejection of modern scientific concepts, such as evolution, that describe the origin and development of natural phenomena.

The term creationism most often refers to belief in special creation: the claim that the universe and lifeforms were created as they exist today by divine action, and that the only true explanations are those which are compatible with a Christian fundamentalist literal interpretation of the creation myth found in the Bible's Genesis creation narrative. Since the 1970s, the most common form of this has been Young Earth creationism which posits special creation of the universe and lifeforms within the last 10,000 years on the basis of flood geology, and promotes pseudoscientific creation science. From the 18th century onward, Old Earth creationism accepted geological time harmonized with Genesis through gap or day-age theory, while supporting anti-evolution. Modern old-Earth creationists support progressive creationism and continue to reject evolutionary explanations. Following political controversy, creation science was reformulated as intelligent design and neo-creationism.

Mainline Protestants and the Catholic Church reconcile modern science with their faith in Creation through forms of theistic evolution which hold that God purposefully created through the laws of nature, and accept evolution. Some groups call their belief evolutionary creationism. Less prominently, there are also members of the Islamic, Jewish, and Hindu faiths, among others, who are creationists. Use of the term "creationist" in this context dates back to Charles Darwin's unpublished 1842 sketch draft for what became On the Origin of Species, and he used the term later in letters to colleagues. In 1873, Asa Gray published an article in The Nation saying a "special creationist" who held that species "were supernaturally originated just as they are, by the very terms of his doctrine places them out of the reach of scientific explanation."

The basis for many creationists' beliefs is a literal or quasi-literal interpretation of the Book of Genesis. The Genesis creation narratives (Genesis 1–2) describe how God brings the Universe into being in a series of creative acts over six days and places the first man and woman (Adam and Eve) in the Garden of Eden. This story is the basis of creationist cosmology and biology. The Genesis flood narrative (Genesis 6–9) tells how God destroys the world and all life through a great flood, saving representatives of each form of life by means of Noah's Ark. This forms the basis of creationist geology, better known as flood geology.

Recent decades have seen attempts to de-link creationism from the Bible and recast it as science; these include creation science and intelligent design.

To counter the common misunderstanding that the creation–evolution controversy was a simple dichotomy of views, with "creationists" set against "evolutionists", Eugenie Scott of the National Center for Science Education produced a diagram and description of a continuum of religious views as a spectrum ranging from extreme literal biblical creationism to materialist evolution, grouped under main headings. This was used in public presentations, then published in 1999 in Reports of the NCSE. Other versions of a taxonomy of creationists were produced, and comparisons made between the different groupings. In 2009 Scott produced a revised continuum taking account of these issues, emphasizing that intelligent design creationism overlaps other types, and each type is a grouping of various beliefs and positions. The revised diagram is labelled to shows a spectrum relating to positions on the age of the Earth, and the part played by special creation as against evolution. This was published in the book Evolution Vs. Creationism: An Introduction, and the NCSE website rewritten on the basis of the book version.

The main general types are listed below.

Young Earth creationists such as Ken Ham and Doug Phillips believe that God created the Earth within the last ten thousand years, with a literalist interpretation of the Genesis creation narrative, within the approximate time-frame of biblical genealogies. Most young Earth creationists believe that the universe has a similar age as the Earth. A few assign a much older age to the universe than to Earth. Young Earth creationism gives the universe an age consistent with the Ussher chronology and other young Earth time frames. Other young Earth creationists believe that the Earth and the universe were created with the appearance of age, so that the world appears to be much older than it is, and that this appearance is what gives the geological findings and other methods of dating the Earth and the universe their much longer timelines.^{[citation needed]}