Dia Art Foundation, American foundation that supports contemporary art and artists, est. 1974 by art dealer Heiner Friedrich and his wife, art patron Philippa de Menil. The foundation, which commissions and purchases artworks, specializes in artists first recognized in the 1960s and 70s and younger artists working within the same aesthetic tradition, and has amassed a significant collection. Dia presents long-term exhibitions and site-specific installations and also funds such activities as lectures, poetry readings, and Web-based projects.

The foundation operates Dia:Beacon (est. 2003), the world's largest contemporary art museum, located in Beacon, N.Y. A converted factory, it contains unusually large unbroken spaces, ideal for exhibiting the frequently monumental and often minimalist (see minimalism) art and large-scale installations Dia favors. For some time (1987–2004), it also maintained exhibition spaces in New York City. The foundation also funds and oversees massive land art and site-specific projects in various parts of the country, such as Robert Smithson's Spiral Jetty in the Great Salt Lake, Utah; Donald Judd's installations at Marfa, Tex.; Michael Heizer's City in Nevada; James Turrell's Roden Crater in Arizona; and Walter De Maria's Lightning Field in New Mexico as well as his New York Earth Room and Broken Kilometer, both in Manhattan (see land art). Dia's permanent collection includes pivotal works by such artists as Joseph Beuys, Louise Bourgeois, John Chamberlain, Dan Flavin, Judd, Agnes Martin, Gerhard Richter, Richard Serra, and Andy Warhol.