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[2] 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.

His proposers were Andrew Douglas Maclagan, Thomas Richard Fraser, Sir Isaac Bayley Balfour, and Charles Hunter Stewart.

I Field Hospital, and was active in operations in the Malakand, in Bajaur, in the Mahmund country, and in Buner, including the action at Laudakai and the attack and capture of the Tanga Pass.

For his services he was made a Companion of the Order of the Bath (abbreviated in postnominal letters to CB) in the October 1902 South African Honours list.

His work was based around the plants he had collected in Afghanistan, Mauritius, Canaries, Madeira, Egypt, Gambia, Natal, India, and Sierra Leone.