The Commonwealth Fund of New York was a major philanthropic foundation established in 1918 by Anna M. Harkness in memory of her husband, Stephen V. Harkness. Based in New York City, it operated for more than seven decades as an independent grantmaking institution and distributed roughly $129 million before ending active operations in 1993. Its work reached well beyond a single field. Over time the fund supported programs in medicine and public health, education, the humanities, and social services, and it became known for backing both institutions and individual advancement. A concrete and enduring part of its legacy was the Commonwealth Fund Fellowship Program. Beginning in 1925, the fund financed overseas study for British citizens at universities in the United States, creating a transatlantic educational exchange that continued for decades. The foundation also sponsored medical fellowships and helped build professional training and research capacity in health-related fields. In New York and nationally, its grants aided hospitals, universities, and cultural and civic initiatives, reflecting a broad philanthropic agenda rather than a narrow scholarship function. The organization’s history is closely tied to the Harkness family’s larger philanthropic record and to twentieth-century foundation development in the United States. Although the original Commonwealth Fund of New York concluded its grantmaking in 1993, its name remains historically significant because of the institutions, fellowships, and public-serving programs it financed over its lifespan. The foundation’s record places it among the notable New York-based philanthropies that used private wealth to strengthen education, health, and social welfare on an international as well as domestic scale.