Ruth Mary Tristram (25 April 1886 – 22 October 1950) was a British amateur botanist.

[1] Born Ruth Mary Cardew on 25 April 1886, married Major Guy H. Tristram (-1963) in 1919, they had four children.

Son Launcelot died aged eight, and Tristram attempted to communicate with him by automatic writing.

Tristram became an expert on Plantago and was elected a fellow of the Linnean Society on 7 December 1911.

She worked with E. G. Barker on Plantago with a plan to publish an account in for Cambridge British Flora.