PARIS — Two art collectors from the United States, Marlene and Spencer Hays, have pledged the Musée d’Orsay here the largest foreign collection of art to be donated to France since World War II — more than 600 masterworks from the late 19th and early 20th centuries, including works by Pierre Bonnard, Edouard Vuillard, Amedeo Modigliani and Henri Matisse.

The couple, both 80 years old, signed an agreement with the French state on Saturday at the Élysée Palace in a ceremony in which President François Hollande named them both commanders of the Legion of Honor.

In 2013, 187 works valued at 173 million euros ($188 million) were shown at the museum in “A Passion for France: The Marlene and Spencer Hays Collection,” an exhibition organized in part by Guy Cogeval, the president of the Musée d’Orsay and Musée de l’Orangerie and a key player in securing the donation.

The works will be transferred to France upon the couple’s deaths, and the Musée d’Orsay has agreed to display their collection intact in a dedicated space in the museum rather than dispersing the works throughout the galleries.