The A4200 is a major thoroughfare in central London. It runs between the A4 at Aldwych, to the A400 Hampstead Road/Camden High Street, at Mornington Crescent tube station, via Holborn, Bloomsbury, Euston and Somers Town.

Kingsway is a major road in central London, designated as part of the A4200. It runs from High Holborn, at its north end in the London Borough of Camden, and meets Aldwych in the south in the City of Westminster at Bush House. It was opened by King Edward VII in 1905. Together Kingsway and Aldwych form one of the major north–south routes through central London linking the ancient east–west routes of High Holborn and Strand. The name "King's Way" originally applied to what is now Theobalds Road, as it was the route that King James I took when travelling from London to his residence Theobalds Palace in Hertfordshire.

The road was purpose-built as part of a major redevelopment of the area in the 1900s. Its route cleared away the maze of small streets in Holborn such as Little Queen Street and the surrounding slum dwellings. However, Holy Trinity Church in Little Queen Street was spared, whereas the Sardinian Embassy Chapel, an important Roman Catholic church attached to the Embassy of the Kingdom of Sardinia, was demolished to make way for the new street.

Plans were published by London County Council in 1898, authorised by the London County Council (Improvements) Act 1899 (62 & 63 Vict. c. cclxvi) and the road was formally opened in 1905. It is one of the broadest streets in central London at 100 feet (30 m) wide. There were several proposed names for the new street, including King Edward VII Street, Empire Avenue, Imperial Avenue and Connecticut Avenue. The name "Kingsway" was in honour of King Edward VII, who opened the street.

It was unique in containing below it a tunnel for a tramway, which started just north of Southampton Row, passed beneath Aldwych and continued to the Thames Embankment; this Kingsway tramway subway joined the North and South London tram systems. In 1958 the disused tunnel was reopened at the southern end to make a new connection, the Strand Underpass, for light traffic between Waterloo Bridge and Kingsway in order to reduce congestion. Also beneath Kingsway was a branch of the Piccadilly tube line from Holborn to Aldwych station on the Strand; this was closed in 1994. Aldwych station is still used for television and film sets that require underground scenes. During the Second World War the branch was used to store art treasures from the British Museum, including the Elgin Marbles.

On 1 April 2015, electrical cables under the pavement in Kingsway caught fire, leading to serious disruption in central London. The fire continued for the next two days, with flames shooting out of a manhole cover from a burst gas main, before being extinguished. Several thousand people were evacuated from nearby offices, and several theatres cancelled performances. There was also substantial disruption to telecoms infrastructure. On 8 April, press reports emerged stating that the fire may have been started as part of the 2015 Hatton Garden burglary; however, the investigation into how the fire started stated on 9 April that it came from an electrical fault.

The original buildings were built between 1903 and 1905. They were mostly mid-rises in stone, and in various styles including neoclassical and neo-Baroque. Many survive but some have been replaced. Notable buildings include:

The closest tube stations are Holborn, which is at the top of the road, at the junction with High Holborn, as well as Temple, and formerly Aldwych, which closed in 1994.