Finchley was a constituency represented in the House of Commons of the Parliament of the United Kingdom. It elected one Member of Parliament (MP) by first-past-the-post voting; its longest-serving and best-known MP was Margaret Thatcher, Prime Minister from 1979 to 1990. Although boundary changes meant that she never again attained the large majority by which she won in 1959, her constituents nonetheless returned her by comfortable (9,000) majorities at general elections throughout her premiership.

The seat was abolished in 1997 and split between the Finchley and Golders Green and Chipping Barnet constituencies.

• 1918–1945: The Urban Districts of Finchley and Friern Barnet.
• 1945–1950: The Municipal Borough of Finchley, part of the Municipal Borough of Hornsey, and part of the Urban District of Friern Barnet.
• 1950–1974: The Municipal Borough of Finchley, and the Urban District of Friern Barnet.
• 1974–1997: The London Borough of Barnet wards of East Finchley, Finchley, Friern Barnet, St Paul's, and Woodhouse.

In 1918 the constituency was created as a county division of Middlesex, centred on the town of Finchley, which before 1918 had been located in the Hornsey constituency. In 1934 the Finchley district became a Municipal Borough.

In 1945 there was an interim redistribution of parliamentary constituencies to split those with more than 100,000 electors, prior to the general redistribution of 1950. Middlesex was significantly affected by the interim changes.

In 1950 the seat was re-classified as a borough constituency, with the boundaries reverting to those of 1918.

In 1965 the area of the constituency changed counties from Middlesex to London. Specifically its areas joined with others to form the London Borough of Barnet of Greater London.