“Woman in an Armchair (Eva)” by Pablo Picasso

In one of the most significant gifts in the history of the Metropolitan Museum of Art, the philanthropist and cosmetics tycoon Leonard A. Lauder has promised the institution his collection of 78 Cubist paintings, drawings and sculptures.

The trove of signature works, which includes 33 Picassos, 17 Braques, 14 Légers and 14 works by Gris, is valued at more than $1 billion. It puts Mr. Lauder, who for years has been one of the city’s most influential art patrons, in a class with cornerstone contributors to the museum like Michael C. Rockefeller, Walter Annenberg, Henry Osborne Havemeyer and Robert Lehman.

The gift was approved by the Met’s board at a meeting Tuesday afternoon.

Scholars say the collection is among the world’s greatest, as good as, if not better than, the renowned Cubist paintings, drawings and sculptures in institutions like the Museum of Modern Art in New York, the State Hermitage Museum in St. Petersburg and the Pompidou Center in Paris. Together they tell the story of a movement that revolutionized Modern art and fill a glaring gap in the Met’s collection, which has been notably weak in early-20th-century art.

“In one fell swoop this puts the Met at the forefront of early-20th-century art,” Thomas P. Campbell, the Met’s director, said. “It is an unreproducible collection, something museum directors only dream about.”

And many did. Discussions between Mr. Lauder and the Met went on for years, first with Philippe de Montebello, its longtime director who retired in 2008, and more recently with Mr. Campbell. While Mr. Lauder declined to say who else courted his collection, officials in the museum world have said the National Gallery of Art in Washington was among them. But as a New Yorker aware that his art could radically transform one of the city’s most historic institutions, he saw the Met as a perfect fit.

“Whenever I’ve given something to a museum, I’ve wanted it to be transformative,” Mr. Lauder explained. “This wasn’t a bidding war. I went knocking, and the door opened easily.”

In the New York art scene, which is heavily populated with big-time collectors, Mr. Lauder is a singular figure. While many of his peers have made splashy acquisitions, seduced by the latest trends, he has quietly and steadily built a museum-worthy collection with a single focus, on Cubism.

Continue reading in TheNewYorkTimes