Greta Barbara Stevenson (10 June 1911 – 18 December 1990) was a New Zealand botanist and mycologist.

William was the managing director of the canned food manufacture Irvine and Stevenson.

[3] After graduating she moved to London to attend the Imperial College of Science and Technology, where she completed a PhD in mycology and plant pathology.

[2] Stevenson was an avid mountaineer, and climbed the east peak of Mount Earnslaw, then a significant accomplishment for an all-woman party.

She is known for her five-part series on the Agaricales of New Zealand, published in the Kew Bulletin between 1962 and 1964, in which she described over 100 new species.