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 | |
|---|---|---|---|
| Adams, Dr. Walter Sydney | USA | 1945 | 1956 |
| Ambartsumian, Dr. Viktor Amazaspovitch | USSR/Armenia | 1959 | 1996 |
| Baade, Dr. Wilhelm Heinrich Walter | Germany | 1954 | 1960 |
| Backlund, Dr. Oskar | Sweden/Russia | 1916 | 1916 |
| Baillaud, Dr. Édouard Benjamin | France | 1916 | 1934 |
| Baldwin, Dr. Ralph Belknap | USA | 1980 | 2011 |
| Ball, Dr. Sir Robert Stawell | United Kingdom | 1894 | 1913 |
| Barnard, Dr. Edward Emerson | USA | 1901 | 1923 |
| Bateson, Dr. Frank M. | New Zealand | 1984 | 2006 |
| Bok, Dr. Bart J. | Holland, USA, Australia | 1961 | 1982 |