Abstractionism can refer to two different concepts: one related to art and the other related to philosophy.

In art, abstractionism refers to a genre of art that does not represent things pictorially, but rather relies on internal form and visual language of shape, form, color, and line to create a composition that may exist with a degree of independence from visual references in the world. Abstractionism in art can be partial or complete, and it exists along a continuum. Even art that aims for verisimilitude of the highest degree can be said to be abstract, at least theoretically, since perfect representation is impossible.

In philosophy, abstractionism is the theory that the mind obtains some or all of its concepts by abstracting them from concepts it already has, or from experience. This theory has its roots in Aristotles writings, particularly those rejecting the Platonic theory of Forms. The doctrine became entrenched in the seventeenth century and was further developed by John Locke, who proposed his own theory of abstract ideas. Modern versions of abstractionism include those developed by theorists such as Noam Chomsky and Jerry Fodor, who proposed that concepts are preformed at birth and that we learn to match the words of our language onto the pre-existing concepts.