| Election Name: | 1981 Croydon North West by-election |
| Type: | parliamentary |
| Country: | United Kingdom |
| Seats For Election: | Constituency of Croydon North West |
| Ongoing: | no |
| Previous Election: | 1979 United Kingdom general election |
| Previous Year: | 1979 |
| Election Date: | 22 October 1981 |
| Candidate1: | Bill Pitt |
| Image1: | Lib |
| Party1: | Liberal Party (UK) |
| Popular Vote1: | 13,800 |
| Percentage1: | 40.0% |
| Swing1: | 29.4% |
| Candidate2: | John Butterfill |
| Party2: | Conservative Party (UK) |
| Popular Vote2: | 10,546 |
| Percentage2: | 30.5% |
| Swing2: | 18.9% |
| Candidate3: | Stanley Boden |
| Image3: | Lab |
| Party3: | Labour Party (UK) |
| Popular Vote3: | 8,967 |
| Percentage3: | 26.0% |
| Swing3: | 14.1% |
| MP | |
| Posttitle: | Subsequent MP |
| Before Election: | Robert Taylor |
| Before Party: | Conservative Party (UK) |
| After Election: | Bill Pitt |
| After Party: | Liberal Party (UK) |
| Turnout: | 62.5% (10.0%) |
| Next Election: | 1983 United Kingdom general election |
| Next Year: | 1983 |
The Croydon North West by-election took place on 22 October 1981. It was caused by the death of Conservative Member of Parliament Robert Taylor on 18 June 1981.
The Conservative Party selected John Butterfill, then vice-chairman of Guildford Conservative Association. The Labour Party, the runners-up at the 1979 general election, selected a local councillor, Stanley Boden.
The Liberal Party had come a distant third in 1979, but the by-election came shortly after the formation of the Social Democratic Party (SDP), with whom the Liberals had entered into an electoral pact, the SDP–Liberal Alliance. It was therefore expected that the election would provide a platform for Shirley Williams of the SDP to return to Parliament, having lost her seat in 1979. However, the Liberal Party insisted on their own candidate and selected the lesser known Bill Pitt who had stood in the seat for the previous three general elections and at the time was the London Regional Party Chair.
The 22-year-old Nick Griffin (who became leader of the British National Party in 1999) stood in his first election in Croydon North West, representing the National Front. Bill Boaks, a road safety campaigner and perennial candidate, was also on the ballot. In total, a record twelve candidates stood, one more than in the 1978 Lambeth Central by-election. This record was broken at the 1984 Chesterfield by-election.
Pitt duly won the seat on the surge of support for the Alliance and a 24% swing, strengthening the Liberals' hand in negotiations with the SDP.
Pitt's win was the Alliance's first electoral success and delighted Liberal leader David Steel who said that the party had won a greater majority than they had expected. Noting that they seemed to have taken support away from both of the main parties in almost equal measure, Steel stated that "I believe that we are now unstoppable."[1] The political editor of The Glasgow Herald, Geoffrey Parkhouse, said the result "shattered" both Labour and the Conservatives and noted that Margaret Thatcher and Michael Foot would fear that the result reflected the victorious Pitt's claim that the Alliance had "caught the imagination of the voters" and that as consequence there were "no longer any safe seats for Tory or Labour in the country."[1] Parkhouse also thought the result made the Alliance favourites to win the forthcoming by-election in Crosby.[1] Pitt was not successful in retaining the seat in the 1983 general election, losing to Conservative candidate Humfrey Malins. At the same general election, the unsuccessful Conservative candidate John Butterfill was elected as the MP for Bournemouth West, a seat he held for 27 years until his retirement in 2010.