Adelaide Helen Grant Sinclair, OC OBE (January 16, 1900 – November 20, 1982) was a Canadian public servant. She was the second Chairman of the UNICEF Executive Board from 1951 to 1952, and from 1957 to 1967, she was the deputy executive director for programs of UNICEF, and one of the highest ranking women at the United Nations. In 1930 she married Donald Black Sinclair, a Toronto lawyer, who died in 1938. The couple had no children. In 1967, she was made an Officer of the Order of Canada. She received an honorary degree from the University of British Columbia in 1968.