Hans-Voldemar Trass (2 May 1928 – 14 February 2017) was an Estonian ecologist and botanist.

In 1992, Trass was awarded the Acharius Medal by the International Association for Lichenology.

[1] Trass was married to Estonian actress Raine Loo.

The couple had a son, composer and organist Toomas Trass.

[2] Trass died in Tartu, Estonia, on 14 February 2017, aged 88.