Lieutenant-Colonel Sir Charles Richard Mackey O'Brien KCMG (13 December 1859 – 29 November 1935) was a British Army officer and colonial administrator.

[1] On 3 September 1878, in company with five other ensigns of his regiment, he was returning from Gravesend to Woolwich following musketry training, but they missed their ferry, the SS Princess Alice, by seconds.

In Gallion's Reach the Princess Alice collided with the steamer SS Bywell Castle and sank with the loss of nearly 700 of her 800 passengers, one of the worst maritime disasters in British history.

He served with the 1st Battalion, East Lancashire Regiment in the Second Boer War, seeing considerable combat and later being appointed president of the military tribunal in Johannesburg, for which he was twice mentioned in dispatches.

He was promoted brevet lieutenant-colonel in the South African honours list published on 26 June 1902,[2] and retired from the Army in March 1903.