Ruth Mason (7 November 1913 – 14 May 1990) was a New Zealand botanist specialising in the taxonomy and ecology of freshwater plants.

[2] In 1939, Mason was appointed to the Department of Scientific and Industrial Research (DSIR) as an assistant botanist.

[1] She joined her colleague, supervisor, and fellow botanist Lucy Moore, who had started at DSIR the previous year.

[2][6] Her research and collections have made major contributions to our understanding of the taxonomy, ecology and distribution of aquatic plants in New Zealand and throughout the world.

[2] Due to her extensive fieldwork, Mason pioneered new techniques for plant preservation in the field, and collected over 13,000 specimens, many of which are housed at the Allan Herbarium at Manaaki Whenua - Landcare Research, Lincoln.

[17] Mason was an avid tramper and was active in the Tararua Tramping Club and Wellington Botanical Society prior to moving to the South Island in 1954, where she lived in Prebbleton (near Christchurch, New Zealand) for almost three decades.

[2] In addition to botany and the outdoors, Mason had wide-ranging interests throughout her life in music, lexicography, history, yoga and working for UNICEF.