Honorary Membership was limited to 10 from 1890-1900, and to 15 from 1901 onwards. Corresponding Membership was a lesser class of Honoris causa membership in the early years. A few honorary members, such as Barnard, were first made corresponding members for a short time before being recommissioned as honorary members.
| Nation(s) | Start | End | |
|---|---|---|---|
| Sandage, Dr. Allan R. | USA | 1975 | 2010 |
| Schlesinger, Dr. Frank | USA | 1916 | 1943 |
| Schwarzschild, Dr. Martin | USA | 1963 | 1999 |
| Shapley, Dr. Harlow | USA | 1947 | 1972 |
| Shearmen, Mr. T.S.H. | Canada | 1890 | 1900 |
| Shklovsky, Dr. Iosif S. | USSR | 1966 | 1984 |
| Shoemaker, Carolyn | USA | 2003 | 2021 |
| Spencer Jones, Sir Harold | United Kingdom | 1947 | 1960 |
| Stebbins, Dr. Joel | USA | 1958 | 1966 |
| Stratton, Prof. Frederick John Marrian | United Kingdom | 1954 | 1960 |