South East England is one of the nine official regions of England at the first level of ITL for statistical purposes. It consists of the counties of Buckinghamshire, East Sussex, Hampshire, the Isle of Wight, Kent, Oxfordshire, Berkshire, Surrey and West Sussex. Major towns and cities in the region include Brighton and Hove, Milton Keynes, Southampton, Portsmouth, Slough, Reading and Oxford.

South East England is the third-largest region of England, with an area of 19,096 km² (7,373 sq mi), and is also the most populous with a total population of over eight and a half million (2011). The region contains eight legally chartered cities: Brighton and Hove, Canterbury, Chichester, Milton Keynes, Oxford, Portsmouth, Southampton and Winchester. The region's close proximity to London and connections to several national motorways have led to South East England becoming a prosperous economic hub with the largest economy of any region in the UK, after London. The region is home to Gatwick Airport, the UK's second-busiest airport, and Heathrow Airport (the UK's busiest airport) is located adjacent to the region's boundary with Greater London. The coastline along the English Channel provides numerous ferry crossings to mainland Europe.

The region is known for its countryside, which includes two national parks: the New Forest and the South Downs, as well as the North Downs, the Chiltern Hills and part of the Cotswolds. The River Thames flows through the region and its basin is known as the Thames Valley. It is also the location of a number of internationally known places of interest, such as HMS Victory in Portsmouth, Cliveden in Buckinghamshire, Thorpe Park and RHS Wisley in Surrey, Blenheim Palace in Oxfordshire, Windsor Castle in Berkshire, Leeds Castle, the White Cliffs of Dover and Canterbury Cathedral in Kent, Brighton Palace Pier, and Hammerwood Park in East Sussex, and Wakehurst Place in West Sussex. The region has many universities; the University of Oxford is the oldest in the English-speaking world, and ranked among the best in the world.

South East England is host to various sporting events, including the annual Henley Royal Regatta, Royal Ascot and The Derby, and sporting venues include Wentworth Golf Club and Brands Hatch. Some of the events of the 2012 Summer Olympics were held in the south east, including the rowing at Eton Dorney and part of the cycling road race in the Surrey Hills.

In medieval times, South East England included much of the Kingdom of Wessex, which was the precursor to the modern state of England. Winchester was the capital of England after unification of the various states, including the kingdoms of Kent, Sussex and Mercia. Winchester stopped being the administrative capital of England some time in the 13th century as its influence waned while the City of London dominated commerce. The last monarch to be crowned at Winchester was Richard II in 1377, although the last monarch to be crowned by the Bishop of Winchester was Queen Mary I in 1553.