Henry Charles Fletcher was born on April 28, 1833, in Marylebone, Middlesex, England.

He was a British military officer, private secretary, and author. In 1850, he obtained a commission as ensign in the Scots Fusilier Guards and as a lieutenant in the army. He saw active service in the Crimea in 1856, and promotion to captain and lieutenant-colonel in 1859. He travelled to Canada with the 2nd Battalion in the Guards brigade at the end of 1861 during strained relations between Great Britain and the United States following the Trent incident. He took the opportunity to see the American Civil War and was present at the battles of Williamsburg, Fair Oaks, and the Seven Days. In 1872, Lord Dufferin was appointed Governor-General of Canada and he chose Fletcher as his private secretary in Ottawa. His chief task was to develop a military spirit in Canada so that the Canadian government might be induced to make adequate provision for defence. He also suggested Canada should train its militia officers in permanent schools. In 1875, he returned to his regiment in England where he was aide-de-camp to the Duke of Cambridge and a justice of the peace in Kent. He lectured to the Royal United Service Institution on the use of colonial forces in imperial wars. He is the author of "The Defence of Canada; a Lecture Delivered at the Literary and Scientific Institute" (Ottawa, 1875); "History of the American War” (3 v., London, 1865–66), and "Memorandum on the Militia System of Canada" (Ottawa, 1873).

In 1863, he married Lady Harriet Marsham (1838–1886). He died on August 31, 1879, in Putney, Surrey, England.