[2] The school was founded in 1572 by John Lyon, a local landowner and farmer, under a royal charter of Queen Elizabeth I.

Its list of distinguished alumni includes seven former British prime ministers: Aberdeen, Perceval, Goderich, Peel, Palmerston, Baldwin and Churchill, as well as the former Indian Prime Minister Jawaharlal Nehru; numerous former and current members of both Houses of the UK Parliament, several members of various royal families, three Nobel Prize winners, twenty Victoria Cross holders, and many prominent figures in the arts and sciences.

The school was founded in February 1572 under a royal charter granted by Queen Elizabeth I to John Lyon, a wealthy local farmer.

[5] The charter described this as a re-endowment, and there is some evidence of a grammar school at Harrow in the mid-16th century, but its location and connection with Lyon's foundation are unclear.

John Lyon's school was founded to provide free education for 30 (later extended to 40) poor boys of the parish.

[8] The majority of the school's boarding houses were constructed in Victorian times, when the number of boys increased dramatically.

[15] Everyday dress for boys at Harrow consists of a dark blue jacket known as a "bluer" with light grey trousers known as "greyers".

School monitors (prefects) may wear black double-breasted waistcoats and a top hat, and carry canes.

The House Master oversees the welfare of every boy in his care; for parents, he is the main point of contact with the School.

The matrons are supported by the School's Medical Centre where trained nursing staff offer round-the-clock care.

Winston Churchill was a great lover of Harrow songs and when he returned for a concert as Prime Minister in 1940, it was the first of many annual visits.

In February 2016, the actor Laurence Fox claimed Harrow threatened legal action to prevent him discussing the racism, homophobia and bullying he said he encountered as a pupil at the school.

Other alumni include writers Lord Byron, Anthony Trollope, Sir Terence Rattigan, Simon Sebag-Montefiore, and Richard Curtis, the Gerald Grosvenor, 6th Duke of Westminster and prominent reformist Anthony Ashley-Cooper, 7th Earl of Shaftesbury, military commanders such as Harold Alexander, 1st Earl Alexander of Tunis and Sir Peter de la Billiere, and business people (including DeBeers chairman Nicky Oppenheimer, Pret a Manger founder Julian Metcalfe) and the big game hunter and artist General Douglas Hamilton, as well as Island Records founder Chris Blackwell.

In sports, the school produced the first two Wimbledon champions (Spencer Gore and Frank Hadow) as well as FA Cup founder C. W. Alcock and current England rugby international players Billy Vunipola, Maro Itoje and Henry Arundell.

Alumni in the arts and media industry include actors Edward Fox, Benedict Cumberbatch and Cary Elwes, photographer Nikolai von Bismarck, singers David Dundas and James Blunt, pianist James Rhodes, horse racing pundit John McCririck, and Mark Thatcher, son of Margaret Thatcher.

Fictional characters who have attended Harrow include Brett Sinclair of the TV series The Persuaders!, Withnail and Uncle Monty from the film Withnail & I,[citation needed] Herbert Pocket from Charles Dickens's novel, Great Expectations,[29] and Geoffrey Charles Poldark from Poldark.