Born in Halifax, Nova Scotia, the sixth child and third son of John Stairs and Mary Morrow, he attended school at Fort Massey Academy in Halifax, Merchiston Castle School in Edinburgh, Scotland, and the Royal Military College of Canada.
After graduating as a trained engineer, Stairs spent three years working for the New Zealand Trigonometrical Survey in northern New Zealand. In 1885, he accepted the offer of a commission in the British Royal Engineers and trained in Chatham, England.
In the tradition of the great Victorian era explorers, on his first mission Capt. Stairs distinguished himself as the British military chief officer, and second in command to Henry Morton Stanley, in the Emin Pasha Relief Expedition.
During two of his three-year journeys across Africa, William Grant Stairs discovered one source of the Nile, the Semliki River, and became the first non-African to ever climb in the Ruwenzoris. In the midst of the first three thousand mile trans-African trek he was seriously wounded by a poisonous arrow in the chest from an attack by warring natives. He would recover from his wound to continue the journey. In Dublin, Ireland there is a bronze plaque depicting this August 13, 1887 event on the statue of expedition Surgeon Major T.H. Parke who removed the arrow and sucked the poison from the wound.
Lauded in Europe and North America for his heroic exploits, on his return to England Capt. Stairs was named a Fellow of the Royal Geographical Society and the Royal Scottish Geographical Society in 1890. In 1891 he transferred to the Royal Welsh Regiment and was then asked by King Leopold II of Belgium to command a mission to take control of the African copper lands of Katanga.
After leading this successful expedition, Capt. Stairs began planning for another mission into the African continent. However, in 1892, a few weeks shy of his twenty-ninth birthday, and suffering from recurring bouts of malaria, he passed away at Chinde, Mozambique.
Upon his passing, memorials were erected at the Royal Military College of Canada and St. George's Cathedral in Kingston, Ontario and in Rochester Cathedral near Chatham, England. A collection of artifacts from his African expeditions are at the McCord Museum, Montreal , Quebec and his diaries are preserved in the Public Archives of Nova Scotia.
His missions are detailed in books, two of which contain Stairs' diaries compiled during the two major expeditions:
Captain Stairs is buried in the European Cemetery in Chinde, Mozambique at the mouth of the Zambezi River.