William Baldwin, Jr. (1903- 25 November 1983), known as Billy Baldwin and nicknamed Billy B, was a New York interior decorator, characterized in an obituary as the "dean of interior decorators". He was named to the International Best Dressed List Hall of Fame in 1974.
Baldwin was born in Roland Park, Maryland and studied architecture at Princeton, dropping out after two years.
Baldwin died in 1983 on Nantucket Island, Massachusetts.
Starting in 1935, he was employed by Ruby Ross Wood, and when she died in 1950, he took over the firm. In 1952, he formed his own firm, Baldwin and Martin, with Edward Martin. They designed the homes and apartments of many well-known people, including the White House of John F. Kennedy. His clients included Cole Porter, Mary Wells Lawrence, Billy Rose, Rachel Lambert Mellon and Paul Mellon, Jacqueline Kennedy Onassis, Mike Nichols, Harvey Ladew, William S. Paley, Barbara Hutton and Diana Vreeland.
In 1972, Billy Baldwin designed a line of furniture. Included in this collection is the famous Slipper Chair; Billy was the original designer of the slipper chair. This collection continues to be manufactured by the Billy Baldwin Studio.
Baldwin retired in 1973.