Honor Oak is an inner suburban area principally of the London Borough of Lewisham, with part in the London Borough of Southwark. It is named after the oak tree on One Tree Hill that Elizabeth I is reputed to have picnicked under.

One Tree Hill is the central feature of Honor Oak's landscape. It is at the northern end of a string of hills stretching from Croydon, previously part of the Great North Wood. A legend tells that on 1 May 1602, Elizabeth I picnicked with Sir Richard Bulkeley of Beaumaris in the Lewisham area by an oak tree at the summit of a hill. The tree came to be known as the Oak of Honor. The tree surrounded by railings is an oak, and was planted in 1905 as a successor to the historic one. In addition to its connection with Queen Elizabeth I, the hill is reputedly the site of the final defeat of Queen Boudica by the Romans in 61AD, while Dick Turpin allegedly used it as a lookout post.

A new development of exclusive houses was started in the 1780s on what is now Honor Oak Road. This gave rise to both Honor Oak and Forest Hill, London communities. These localities have drifted about a mile apart North and South respectively since, aided by the arrival of a canal and then railways.

Between 1809 and 1836, a canal ran through Honor Oak as part of its route from New Cross to Croydon. It also went via Forest Hill and Sydenham. The canal was replaced by a railway line after 1836, and this now forms part of the line between London Bridge and Croydon. Honor Oak Park railway station opened in 1886 on this line. Honor Oak railway station was opened in 1862 but closed in 1958 as part of the closure of the Crystal Palace and South London Junction Railway, originally built to take passengers to The Crystal Palace. The remains of the embankment of this line can still be seen, forming part of Brenchley Gardens.

The beacon at the summit of One Tree Hill was erected to commemorate the Silver Jubilee of King George V in 1935. It was subsequently used for the Coronation of Queen Elizabeth II, her silver and golden jubilees and also at the Millennium. Beacons on the same site were used to give warning of invasion by the Spanish and later the French. The Hill was also the site of Watson's General Telegraph, a relay system established in 1841 linking London with shipping in the English Channel ^{[citation needed]}

Honor Oak & Forest Hill Golf Club (now defunct) was founded in 1893. The club disappeared at the time of WW2. This area is now Camberwell New Cemetery.

In 1896, One Tree Hill was due to become part of a golf club, but there were riots and demonstrations by local people. This fell through, and later it was bought by Metropolitan Borough of Camberwell and made into a public open space by 1905.

During World War I a gun emplacement was erected on the hill to counter the threat of raids by Zeppelin airships.