| Professor Dr Rudolf Kassel FBA | Year of birth 1926 | Year of death 2020 | Year elected 1973 | Fellowship category Corresponding |
| Professor Michael Kauffmann FBA | Year of birth 1931 | Year of death 2023 | Year elected 1987 | Fellowship category UK Emeritus |
| Professor Simon Keay FBA | Year of birth 1954 | Year of death 2021 | Year elected 2016 | Fellowship category UK |
| Professor Elie Kedourie CBE, FBA | Year of birth 1926 | Year of death 1992 | Year elected 1975 | Fellowship category UK |
| Dr Maurice Keen OBE, FBA | Year of birth 1933 | Year of death 2012 | Year elected 1990 | Fellowship category UK Emeritus |
| Professor George Keeton FBA | Year of birth 1902 | Year of death 1989 | Year elected 1964 | Fellowship category UK |
| Professor Paul Kehr FBA | Year of birth 1860 | Year of death 1944 | Year elected 1938 | Fellowship category Corresponding |
| Professor Dr Joses Keil FBA | Year of birth 1900 | Year of death 1900 | Year elected 1962 | Fellowship category Corresponding |
| Professor Arthur Berriedale Keith FBA | Year of birth 1879 | Year of death 1944 | Year elected 1935 | Fellowship category UK |
| Professor Yuriy Keldish FBA | Year of birth 1900 | Year of death 1995 | Year elected 1976 | Fellowship category Corresponding |
| Professor Dr Hermann Kellenbenz FBA | Year of birth 1900 | Year of death 1994 | Year elected 1977 | Fellowship category Corresponding |
| Professor Morton Keller FBA | Year of birth 1929 | Year of death 2018 | Year elected 1999 | Fellowship category Corresponding |
| Dr John Kelly FBA | Year of birth 1909 | Year of death 1997 | Year elected 1965 | Fellowship category UK |
| Professor Hans Kelsen FBA | Year of birth 1881 | Year of death 1973 | Year elected 1967 | Fellowship category Corresponding |
| Professor Barry Kemp FBA | Year of birth None | Year of death 2024 | Year elected 1992 | Fellowship category UK Emeritus |
| Sir Maurice Kendall FBA | Year of birth 1907 | Year of death 1983 | Year elected 1970 | Fellowship category UK |