Museums are lucky if they receive either a large collection of valuable artworks or a big check. Getting both at the same time is rare.

The Clark Art Institute in Williamstown, Mass., is announcing this week that it has received the rare twofer gift from the Aso O. Tavitian Foundation: a trove of 331 works by revered European artists of the 15th through the 19th centuries — including Hans Memling, Peter Paul Rubens, Parmigianino, Elisabeth Louise Vigée Le Brun, Jean-Antoine Watteau and Gian Lorenzo Bernini — plus more than $45 million to build a new wing to house it all and care for it, and to fund a new curator’s position.

“It’s an unbelievable thing that’s happening to the Clark,” the museum’s director, Olivier Meslay, said, adding that it was the “most transformational gift” since the founding bequest from the collectors Sterling and Francine Clark, for whom the museum is named.

The value of the gift — 132 paintings, 130 sculptures, 39 drawings and 30 decorative arts objects — is likely several hundred million dollars, said Candace Beinecke, president of the Tavitian Foundation.

“He had princely taste,” Meslay said of Tavitian. “He was extremely refined.”

Tavitian, a philanthropist who died in 2020 at age 80, was born in Bulgaria of Armenian descent, immigrated to the United States in 1961 and made a fortune in software. He lived in New York City and Stockbridge, Mass., also in the Berkshires, and developed a deep relationship with the Clark. Tavitian, who began collecting in 2004, served on the Clark’s board of trustees and showed some of his personal holdings there in a 2011 exhibition.