Illusionism in art history means either the artistic tradition in which artists create a work of art that appears to share the physical space with the viewer or more broadly the attempt to represent physical appearances precisely – also called mimesis. The term realist may be used in this sense, but that also has rather different meanings in art, as it is also used to cover the choice of ordinary everyday subject-matter, and avoiding idealizing subjects. Illusionism encompasses a long history, from the deceptions of Zeuxis and Parrhasius to the works of muralist Richard Haas in the twentieth century, that includes trompe-l'œil, anamorphosis, optical art, abstract illusionism, and illusionistic ceiling painting techniques such as di sotto in sù and quadratura. Sculptural illusionism includes works, often painted, that appear real from a distance. Other forms, such as the illusionistic tradition in the theatre, and Samuel van Hoogstraten's "peepshow"-boxes from the seventeenth century, combine illusionistic techniques and media.

Op art, short for optical art, is a style of visual art that uses optical illusions.