Adrienne Arsht, left, Roger Sant and David Rubenstein socialize at a National Symphony Orchestra opening.

Roger Sant, a well-known Washington philanthropist, and his wife, Victoria, have given $10 million to the National Museum of Natural History to endow its director’s post, the Smithsonian Institution announced Tuesday.

Sant said he was impressed with the improvements at the museum in recent years.

“Both Vicki and I are thrilled at what has happened. It is not only the museum side, starting with the Mammals Hall, the Ocean Hall and, soon, the Dinosaur Hall. On the science side, there are so many good ideas, with ‘Recovering Voices’ on the anthropology side and the ‘Encyclopedia of Life.’ ”

Sant said his positive relationship with the director, Cristian Samper, also prompted the gift. “Cristian and I had such a terrific relationship during the hard times when he was acting secretary,” Sant said.

Samper, who is leaving the museum at the end of July, became acting secretary of the Smithsonian after the turbulent investigation and resignation of Lawrence M. Small.

Samper will become president and chief executive of the Wildlife Conservation Society in New York. “So this gift, in a way, is thanks to him,” Sant said.

During Samper’s nine-year tenure at the museum, he raised more than $294 million.

To date, Sant, who is a member of the Smithsonian Board of Regents and vice chair of the Natural History Museum advisory board, has given $35 million to the museum. He contributed a total of $25 million in 2005 and 2008 for the development of an ocean initiative. Victoria Sant, a leader in global population and environmental issues, is president of the board of the National Gallery of Art.

The new gift signals that private funding is rebounding after the 2008 recession, at least at the Natural History Museum. This year, David H. Koch gave $35 million for the renovation of the Dinosaur Hall, and Life Technologies gave $3 million for the development of a future genome exhibition.