John Joseph Aloysius Colahan (30 March 1836 – 19 November 1918) was Surgeon Major General in the British Army.
He married Eliza McDowell Orr (1859–1899), a concert pianist, in Malta, in 1885.
at Queen's University, Galway in 1857, and served as an army surgeon in India, Gibraltar and Malta.
[citation needed] Colahan served as Principal Medical Officer in Ireland.
The family moved from Dublin to Cape Town in 1889, then to Victoria, Australia in 1896.