Highgate School, formally Sir Roger Cholmeley's School at Highgate, is a co-educational, fee-charging, private day school, founded in 1565 in Highgate, London, England. It educates over 1,400 pupils in three sections – Highgate Pre-Preparatory School (ages 4–8), Highgate junior school (ages 8–11) and the senior school (11+) – which together comprise the Highgate Foundation. As part of its wider work the charity was from 2010 a founding partner of the London Academy of Excellence and it is now also the principal education sponsor of an associated Academy, the London Academy of Excellence Tottenham, which opened in September 2017. The principal business sponsor is Tottenham Hotspur FC. The charity also funds the Chrysalis Partnership, a scheme supporting 26 state schools in six London boroughs.

The foundation is governed in accordance with a Charity Commission Scheme dated 1 September 2005 (and amended in 2014). Its governing body consists of 16 members; four are nominated (one each by the universities of Oxford and London, by the Bishop of London, and by the Lord Chief Justice), and the rest are co-opted. The Visitor is Queen Elizabeth II. The head is assisted by principals of the pre-prep and junior schools, by deputy heads and a bursar, in managing the foundation. The school is a member of HMC and IAPS and is one of the twelve schools of the Eton Group.

Cholmeley, a former Chief Justice and local landowner, decided to found a charitable school "for the good education and instruction of boys and young men" in Highgate and the local parishes. On 27 April 1565 he was granted by Edmund Grindal, the Bishop of London, some land on the site of the old gatehouse to the Bishop's Park and Hermit's Chapel (opposite the Gatehouse Inn, which still exists). A new chapel and buildings for the school and the local curate, who was expected to be the teacher, were built. The chapel also served as a chapel of ease for Highgate residents.

However, by the early nineteenth century a dispute arose because the charity was spending more money, and the curate more time, on the local chapel than on the pupils. A House of Commons commission visited in 1819 and found the master, Samuel Mence, was paying a sexton to teach the boys. In a long and bitter action brought in the High Court against the trustees, it was contended that this was contrary to its founding charitable deed. Lord Chancellor Eldon, in his 1827 judgment, agreed, finding "the charity is for the sustenance and maintenance of a free Grammar school". The trustees were forced to comply and a separate local church for Highgate, St Michael's, was built in South Grove after a successful local appeal. Mence struggled on at the school until 1838 when there were only 19 pupils.

An expansion of the school occurred under the next headmaster John Bradley Dyne (Fellow of Wadham College, Oxford) between 1838 and 1874. Under Dyne, by the 1870s the school had largely dropped free provision for local parish boys and alongside the day places boarding was encouraged for boys from the upper and upper middle classes; fees were introduced and academic standards improved. In the period up to this time the school was known commonly as the Free Grammar School at Highgate, the Highgate Grammar School, or the Cholmeley School. Like other public schools, Highgate followed Arnold at Rugby School in introducing the house system. Also, like other public schools, Dyne flogged the pupils with a birch rod.

In the 1860s, land was acquired in Bishopswood Road, which provided extensive sports fields and on which several boarding houses and private residences were built. During this period the current chapel and main buildings were erected, designed by Reginald Blomfield (who had also designed Lady Margaret Hall, Oxford). A fragment of the older school building, a gateway with a rusted bell mechanism above between the porter's lodge and the main school building, remained intact until 2006 when the bell was refurbished and the old entrance itself rebuilt in a more modern style. The senior school continues to occupy today the island site in Highgate Village on which it was founded.

When J. A. H. Johnston was appointed as headmaster in 1908, he found a school with a strong focus on a classical education. He created fifth and sixth forms for science, in which the main subjects were chemistry, physics, biology, and astronomy. In 1928 came the opening of a new Science Building by Sir Samuel Hoare, Secretary of State for Air, and Johnston then introduced aeronautics as a school subject, acquiring a Sopwith Snipe and an Avro 504K biplane.

During the Second World War the school's buildings were commandeered by the British government and the school was evacuated to Westward Ho! in Devon, returning to Highgate in 1943.^{[citation needed]}