Hornsey was a constituency that returned one Member of Parliament (MP) to the House of Commons of the UK Parliament, 1885 — 1983. It was then largely replaced by Hornsey & Wood Green. Its voters using the first-past-the-post system elected the Conservative Party candidate at each election. Its closest result was a 1.29% majority at the 1966 election which saw the start of the Second Wilson Ministry. From 1945 onwards the runners-up in the seat were the Labour Party candidates.

Middlesex was a constituency of the House of Commons of the Parliament of England, then of the Parliament of Great Britain from 1707 to 1800, then of the Parliament of the United Kingdom from 1801 until abolished in 1885. It returned two members per election by various voting systems including hustings.