Reinhard Rudolf Karl Hartmann (8 April 1938 – 12 September 2024) was an Austrian-born English lexicographer and applied linguist. Until the 1970s, lexicographers worked in relative isolation, and Hartmann was credited with making a major contribution to lexicography and fostering interdisciplinary consultation between reference specialists.
R. R. K. Hartmann was co-author of the standard texts Dictionary of Language and Linguistics (1972) and the Dictionary of Lexicography (1998); the former has been translated into Chinese, the latter into Japanese. Hartmann also produced works on a wide range of linguistic and lexicographic topics (see list of Publications below). Two selections of his essays were published in Kuwait (2004) and Germany (2007).