Colonel Henry Halcro Johnston CB CBE DL FRSE FLS (13 September 1856 – 18 October 1939) was a Scottish botanist, physician, rugby union international and Deputy Lieutenant for Orkney.
As a member of Edinburgh University RFC he represented Scotland in 1877 and went on to make a significant contribution to botany and horticulture through his meticulous collection and recording of plant species during and after his distinguished military career.