Ileana Sonnabend (née Schapira, October 28, 1914, Bucharest, Romania - October 2007, New York City) was a dealer of 20th century art.
Her father, a successful businessman, was the financial counselor of King Carol II of Romania. Sonnabend was, for many years, married to Leo Castelli who she met in Bucharest in 1932 and married soon after. The couple had a daughter, Nina Sundell. They went in 1935 to Paris, then she and her husband left Europe in 1941 and settled in New York City.
In 1957 she opened her first art gallery in New York, where exhibited works by Piet Mondrian, Jackson Pollock, Jasper Johns, Robert Rauschenberg. She promoted new artistic trends as Neo-Dada art and Pop Art, showing works by Roy Lichtenstein, Andy Warhol, Claes Oldenburg and James Rosenquist. She ran a contemporary art gallery in Paris during the early 1960s. After leaving Paris, she opened a Sonnabend Gallery in New York City in 1971, at 420 West Broadway, in SoHo, and will make a habit of promoting new forms of art (Minimalism, Arte povera, Conceptual art, Performance, Transavanguardia, Neo-Expressionism, Neo-Geo, New photography) both on Europe and America.
In the late 1999s, the gallery moved to Chelsea and continued to be active until Sonnabend's death. After the death of Ileana, some work in Sonnabend Collection were traded in two auction sales which totaled $ 600 million. The event is considered "the largest private sale of art ever (NY Times)".