As a result of the London Government Act 1963, the borough was formed in 1965 from the Municipal Borough of Finchley, the Municipal Borough of Hendon, the Friern Barnet Urban District of Middlesex and East Barnet Urban District and Barnet Urban District of Hertfordshire. The Act did not include a name for the new borough. A joint committee of the councils due to amalgamate suggested "Northgate" or "Northern Heights". According to the Minister of Housing and Local Government, Keith Joseph, the name Barnet is derived from the Old English word brnet and means "land cleared by burning.".
In the modern borough, evidence of Roman pottery manufacturing has been found at Brockley Hill and Roman coins from Burnt Oak, both of which date from the third and fourth centuries. On the Roman road Watling Street, which now forms the western border of the borough, both sites are located between London (Londinium) and St Albans (Verulamium).
The Domesday Book of 1086 mentions Hendon, but does not mention Barnet, Edgware, or Finchley, possibly because they were included in other manors.
The Battle of Barnet was fought at Monken Hadley in 1471, just within the present-day boundaries of the borough, when Yorkist troops led by King Edward IV killed Richard Neville, Earl of Warwick and his brother, John Neville, 1st Marquess of Montagu.
At the time of its creation, Barnet included part of Elstree, but on 1 April 1993, some of its more rural northern parts, including Elstree, were transferred to Hertfordshire (and its district of Hertsmere).
There are several articles that describe the history and development of the areas of Church End, East Finchley, Edgware, Golders Green, and North Finchley.
The professional football club, Barnet F.C., is located in the borough, as are Wingate & Finchley F.C., Hendon F.C., London Lions and Edgware Town among the non-League clubs. In addition to Hendon and Edgware, Barnet F.C. also plays in the Borough of Harrow. Wingate is the last of these with a home ground in the Borough.
Saracens F.C. have been based in the borough since 2013, playing matches at StoneX Stadium at Barnet Copthall, which used to be a community sports stadium but is still used in this capacity due to Saracens' use of movable stands. The complex also offers athletics facilities and swimming pools.
The borough covers a group of hills on the northern edge of the London Basin. The bedrock is chalk which is covered with clay. Some of the hills are formed from glacial till deposited at the farthest extent of glaciers during the Anglian glaciation.
In the north of the borough on the eastern side is Barnet, also known as High Barnet or Chipping Barnet, Totteridge, and Whetstone. In the north on the western side is Edgware and Mill Hill. The In the central northern part of the borough, there is largely countryside. Due to the expansion of the High Barnet Underground branch of the Northern line on the eastern side, the western side grew around the Midland Railway and Edgware.
Around the borough's centre and the suburbs of Cricklewood, Colindale, Hendon and Finchley, development becomes steadily more intense. Along with Hampstead Garden Suburb and Childs Hill, Golders Green forms the south of the borough and is known for its Jewish minority ethnic population.
Many of the borough's parks and open spaces are within the Metropolitan Green Belt. A large part of the area is taken up by cemeteries and golf courses, as well as Hampstead Heath, Hampstead Heath Extension and Golders Hill Park. Nine of Barnet's 16 main open spaces have been awarded the Green Flag Award for 2008–2009.
There are 67 Sites of Importance for Nature Conservation in the borough, eight Local Nature Reserves, as well as the Wales Harp (Brent) Reservoir, a Site of Special Scientific Interest, jointly managed by the borough and the London Borough of Brent. Nature reserves in Barnet list these.
Barnet shares the A5 (Edgware Road) with Brent and Harrow, except for the West Hendon area and the Welsh Harp.
With a population of 6,404 in 1801, the modern borough was primarily populated by farms and woodlands around the Great North Road. A turnpike was constructed in 1830, and horse-drawn omnibuses were introduced along with it.
As trams and railways arrived in the middle of the 19th century, the population increased dramatically, and new estates were built to house commuters. After industry relocated from London during the 1960s, the population declined, but new brownfield developments have begun to reverse the trend.
During the 2001 census, the borough had a population of 314,564. The latest ONS projection for 2008 indicates a population of 331,500. Sixty-seven percent of the residents are owner-occupied. 47.3% of the local population identified themselves as Christians, while 14.8% identified themselves as Jews. This is the highest percentage of any local authority in the United Kingdom. 12.8% of people said they had no religion, which was the third largest group.
As of the 2011 census, just over a quarter of people belonged to non-white ethnic groups, up from 18% in 1991. 12.3% were Asians and 6.0% were black. Barnet has the largest Chinese population of any London borough with 6,379.
As of 2011, 13.3% of the borough's population is over 65 - the sixth-highest of London's boroughs. The 65+ population is 47,400, the second-highest after Bromley. The Jewish population is 54,084 and represents 15.5% of the population - the highest in the United Kingdom. 41.2% identify themselves as Christians, and 16.1% with no religion.
There were 69,700 households in Barking and Dagenham in 2011, an increase of 3.6% from 2001. The 65+ population has decreased by almost 20% between 2001 and 2011. Among all local authorities in England and Wales, the borough had 21.4% of its population is school-aged (5-19). During the period 2001-2011, the pre-school population in the borough rose by 49.1%, the largest increase in London.