Lieutenant-General Guy Granville Simonds, CC, CB, CBE, DSO, CD (April 23, 1903 – May 15, 1974) was a senior Canadian Army officer who served with distinction during World War II. Acknowledged by many military historians and senior commanders, among them Sir Max Hastings and Field Marshal Sir Bernard Montgomery, as one of the best Canadian generals of the war, Simonds, after serving the first few years of the Second World War mainly as a staff officer, commanded the 1st Canadian Infantry Division with distinction in Sicily and Italy from July 1943 until January 1944, and later II Canadian Corps during the Battle of Normandy from June−August 1944 and throughout the subsequent campaign in Western Europe from 1944, towards the end of which he temporarily commanded the First Canadian Army during the Battle of the Scheldt, until victory in Europe Day in May 1945. The historian J. L. Granatstein states about Simonds: "No Canadian commander rose higher and faster in the Second World War, and none did as well in action. Simonds owed his success wholly to his own abilities and efforts—and those of the men who served under him".

After the end of the war, he went to the Imperial Defence College (IDC) in London, initially as a student and later as an instructor, before returning to Canada to command the National Defence College, Canada. In 1951, at the age of just 48, he was appointed Chief of the General Staff (CGS), the head of the Canadian Army, a post he held for four years, including during the Korean War, before retiring in 1955.

Guy was born in Ixworth, near Bury St Edmunds, Suffolk, England on April 24, 1903.

Simonds came from a military family: his great-grandfather had been in the army of the Honourable East India Company, his grandfather had been a major-general in the British Indian Army and his father an officer in the British Army's Royal Regiment of Artillery. The Simonds family was related to Ivor Maxse and Lord Milner. On his maternal side, his grandfather William Easton was a wealthy Virginian horse breeder, who had moved to England, renting Ixworth Abbey. Eleanor "Nellie" Easton, his mother, was one of five daughters, four of whom married army officers.

His father Cecil, a major, resigned from the British Army in fall 1911 (when Guy was 8) and moved his family to British Columbia, working as a surveyor for a railway. Cecil's expectations of having his own survey company were frustrated by the requirement to pass local professional examinations. Re-joining the army at the start of World War I, Cecil was wounded in 1918, and demobilized in 1919 with the rank of colonel. The family spent the war in a rented house in Victoria. Guy's mother sold family possessions to make ends meet. Guy had to quit school for two years at age fourteen to help support the family. Graham speculates that the period of fatherlessness made him a "loner" and self-reliant.

Simonds had three siblings, Cicely, Peter and Eric. Eric (anecdotally an excellent rifle shot, having won prizes at Bisley) became a test pilot, but died in an air accident off Felixstowe in July 1937 in a Miles Magister while serving with the A&AEE in England. Cicely worked as a secretary in the Admiralty during the war. She and her daughter were killed by a V-1 (flying bomb) attack in June 1944, during World War II.

Simonds attended Collegiate School in Victoria and then Ashbury College in Ottawa beginning in 1919. The college's dining hall is named after him.

He studied at the Royal Military College of Canada in Kingston, Ontario between 1921 and 1925, cadet number 1596. Simonds' class was the last to be selected from nationwide exams (Simonds having been placed second) and the first after the recently ended First World War to enter a four-year course. At graduation he was awarded the Sword of Honour, judged the best "all rounder", placed second academically, and was generally considered the best horseman in the class.