Hans-Voldemar Trass (2 May 1928 – 14 February 2017) was an Estonian ecologist and botanist. He was a member of the Estonian Academy of Sciences from 1975 until his death. He was the president of the Estonian Naturalists' Society from 1964 to 1973 and 1985 to 1991. He was awarded the Acharius Medal by the International Association for Lichenology in 1992.