Harold Gordon Cornell was born on 10 August 1891 at Richmond, Victoria, one of five children born to George Cornell and Sarah Cornell (née Wright). He was educated at Scotch College at Melbourne and graduated in 1913 as an electrical engineer. On 10 September 1916, Harold married Jessie Millicent De Bomford at Saint Martin’s Anglican Church at Queenstown, Tasmania. They had one daughter named Winifred Ella Cornell who was born on 27 June 1917.

Cornell enlisted in the Australian Flying Corps on 15 August 1916 at Claremont, Tasmania and was assigned to 2nd Australian Flying Squadron at Laverton. He embarked from Melbourne on board HMAT Ulysses on 25 October 1916, and two months later, he disembarked at Plymouth in England and commenced training with the Royal Flying Corps.

Cornell was appointed to 2nd Air Mechanic with the newly formed 69th Australian Squadron on 11 January 1917. One month later, he completed training to become a wireless operator and was promoted to the rank of corporal. He was appointed sergeant in August 1917, and shortly thereafter, detached for duty with 30th Training Squadron where he learnt how to fly DH-5 aircraft. Cornell graduated as Flying Officer on 27 October 1917 and left for France.

On 30 November 1917, Cornell left the aerodrome for a special mission over Bourlon Wood, when his aircraft was shot down by enemy aircraft. He miraculously escaped capture after crash landing in a heavily shelled position and managed to find his way back to the aerodrome. The following month, however, he was not so lucky. On 11 December, according to the unit diary, Cornell was testing an aircraft at Baizieux on the Somme when he took a flat turn, stalled, nose-dived at 500 feet, and crashed. Cornell was killed instantaneously and his body was taken to the 56th Casualty Clearing Station.

Harold Gordon Cornell was buried and is commemorated at Dernancourt Communal Cemetery Extension in France.