Sir Joseph Barcroft CBE FRS[1] (26 July 1872 – 21 March 1947) was a British physiologist best known for his studies of the oxygenation of blood.

[2] Born in Newry, County Down into a Quaker family, he was the son of Henry Barcroft DL and Anna Richardson Malcomson of The Glen, Newry – a property purchased for his parents by his mother's uncle, John Grubb Richardson and adjoining his own estate in Bessbrook.

For example, during the First World War, when he was called to Royal Engineers Experimental Station (near Salisbury) to carry out experiments on asphyxiating gas, he exposed himself to an atmosphere of poisonous hydrogen cyanide.

On another occasion he remained for seven days in a glass chamber in order to calculate the minimum quantity of oxygen required for the survival of the human organism, and another time he exposed himself to such a low temperature that he collapsed into unconsciousness.

He also studied the physiology of oxygenation at extreme altitudes, and for this purpose he organized expeditions to the peak of Tenerife (1910), to Monte Rosa (1911), and to the Peruvian Andes (1922).