In January, rumors swirled that the art collector and patron Agnes Gund had sold her prized 1962 Roy Lichtenstein “Masterpiece” for a whopping $150 million, placing it among the 15 highest known prices ever paid for an artwork.

Ms. Gund is confirming that sale now, revealing that she parted with the painting (for what was actually $165 million, including fees) for a specific purpose: to create a fund that supports criminal justice reform and seeks to reduce mass incarceration in the United States.

This new Art for Justice Fund — to be announced Monday at the Museum of Modern Art, where Ms. Gund is president emerita — will start with $100 million of the proceeds from the Lichtenstein (which was sold to the collector Steven A. Cohen through Acquavella Gallery).

“This is one thing I can do before I die,” Ms. Gund, 78, said in an interview at her Upper East Side apartment, where the Lichtenstein used to hang over the mantel, along with works by Jasper Johns and Mark Rothko. “This is what I need to do.”