Daniel Leopold Wildenstein (11 September 1917 – 23 October 2001) was a French art dealer, historian and owner-breeder of thoroughbred and standardbred race horses. He was the third member of the family to preside over Wildenstein & Co., one of the most successful and influential art-dealerships of the 20th century. He was once described as "probably the richest and most powerful art dealer on earth."

Wildenstein was born in Verrières-le-Buisson, Essonne to Jeanne "Jane" (née Lévy) and Georges Wildenstein. He was educated at Cours Hattemer and at the University of Paris, graduating in 1938 and going on to study at the École du Louvre.

Wildenstein's grandfather, Nathan Wildenstein, established an art dealership on the Rue La Boétie in Paris after fleeing his native Alsace during the Franco-Prussian War of 1870/71. He first specialised in 18th-century French painting and sculpture, later expanding to Italian, Dutch, Flemish and Spanish art. Although he had been working in a tailor's shop when he began to trade in art he proved extremely successful, selling to European collectors such as Edmond James de Rothschild and later to Americans such as J. P. Morgan, Henry Clay Frick, and to the Kress, Rockefeller, and Mellon families. He opened a New York gallery in 1903 and one in London in 1925.

The Wildensteins gained a reputation as shrewd businessmen, stockpiling works to maximise their profits when released onto the market. Nathan built a huge inventory of European Old Master paintings, sculpture, drawings, furniture and decorative objects, to which Daniel's father, Georges, added Impressionist and Postimpressionist works. In 1978 Wildenstein & Co's New York storeroom included 20 pictures by Renoir, 25 Courbets, 10 Van Goghs, 10 Cézannes, 10 Gauguins, 2 Botticellis, 8 Rembrandts, 8 Rubens, 9 El Grecos and 5 Tintorettos among a total inventory of 10,000 paintings. The secrecy attached to these holdings led to a great deal of interest and speculation in the art world.

In 1940 Daniel Wildenstein went to New York to work for the family firm. He had already acted as Group Secretary of the French Pavilion at the World's Fair in 1937 and as exhibitions director at the Chaalis museum and its related Jacquemart-Andre Museum. He took over the running of Wildenstein & Co.'s Paris and New York branches in 1959 and those in London and Buenos Aires in 1963, the year his father died. A gallery in Tokyo was added in the early 1970s. As an art dealer Wildenstein was phenomenally successful. A 1998 profile of the family in Vanity Fair magazine asserted that his wealth was estimated at more than $5 billion. "His fortune," the magazine stated, "was the only one of that magnitude ever made in the art market."

Like his father, Daniel Wildenstein established a reputation as a scholar and art historian. He revised and enlarged the catalogues published by his father and began work on his own projects, investing in the acquisition of archival material and establishing the Wildenstein Institute to issue catalogues raisonné which became the authority for authenticating the works of major French artists. His five-volume catalogue raisonné of the work of Claude Monet was published between 1976 and 1992. His two-volumes on Édouard Manet appeared in 1976 and 1977, those on Gustave Courbet in 1977 and 1977, and a book on Paul Gauguin in 2001. He acted as editor-in-chief of the Gazette des Beaux-Arts from 1963 and in 1971 was elected a member of the Académie des Beaux-Arts.

Although he officially retired in 1990, Wildenstein is reported to have maintained a close control over the running of the business. The number of Wildenstein galleries around the world shrank in his later years until it contained only two: Wildenstein & Co. and PaceWildenstein, both in New York. PaceWildenstein was established in 1993 as a joint venture with the Pace Gallery to deal in contemporary art. The collaboration came to an end in 2010.

In 1999 Wildenstein published a series of his interviews entitled Marchand d’Art.