Gradualism, from the Latin gradus ("step"), is a hypothesis, a theory or a tenet assuming that change comes about gradually or that variation is gradual in nature and happens over time as opposed to in large steps. Uniformitarianism, incrementalism, and reformism are similar concepts.

Gradualism can also refer to desired, controlled change in society, institutions, or policies. For example, social democrats and democratic socialists see the socialist society as achieved through gradualism.

In the natural sciences, gradualism is the theory which holds that profound change is the cumulative product of slow but continuous processes, often contrasted with catastrophism. The theory was proposed in 1795 by James Hutton, a Scottish geologist, and was later incorporated into Charles Lyell's theory of uniformitarianism. Tenets from both theories were applied to biology and formed the basis of early evolutionary theory.^{[citation needed]}

Charles Darwin was influenced by Lyell's Principles of Geology, which explained both uniformitarian methodology and theory. Using uniformitarianism, which states that one cannot make an appeal to any force or phenomenon which cannot presently be observed (see catastrophism), Darwin theorized that the evolutionary process must occur gradually, not in saltations, since saltations are not presently observed, and extreme deviations from the usual phenotypic variation would be more likely to be selected against.

Gradualism is often confused with the concept of phyletic gradualism. It is a term coined by Stephen Jay Gould and Niles Eldredge to contrast with their model of punctuated equilibrium, which is gradualist itself, but argues that most evolution is marked by long periods of evolutionary stability (called stasis), which is punctuated by rare instances of branching evolution.

Phyletic gradualism is a model of evolution which theorizes that most speciation is slow, uniform, and gradual. When evolution occurs in this mode, it is usually by the steady transformation of a whole species into a new one (through a process called anagenesis). In this view no clear line of demarcation exists between an ancestral species and a descendant species, unless splitting occurs.

Punctuated gradualism is a microevolutionary hypothesis that refers to a species that has "relative stasis over a considerable part of its total duration [and] underwent periodic, relatively rapid, morphologic change that did not lead to lineage branching". It is one of the three common models of evolution. While the traditional model of palaeontology, the phylogenetic model, states that features evolved slowly without any direct association with speciation, the relatively newer and more controversial idea of punctuated equilibrium claims that major evolutionary changes do not happen over a gradual period but in localized, rare, rapid events of branching speciation. Punctuated gradualism is considered to be a variation of these models, lying somewhere in between the phyletic gradualism model and the punctuated equilibrium model. It states that speciation is not needed for a lineage to rapidly evolve from one equilibrium to another but may show rapid transitions between long-stable states.

In politics, gradualism is the hypothesis that social change can be achieved in small, discrete increments rather than in abrupt strokes such as revolutions or uprisings. Gradualism is one of the defining features of political liberalism and reformism.