| William Henry Flanagan | |
| Constituency Mp: | Manchester Clayton |
| Parliament: | United Kingdom |
| Term Start: | 15 November 1922 |
| Term End: | 6 December 1923 |
| Predecessor: | John Edward Sutton |
| Successor: | John Edward Sutton |
| Term Start2: | 27 October 1931 |
| Term End2: | 14 November 1935 |
| Predecessor2: | John Edward Sutton |
| Successor2: | John Jagger |
| Birth Date: | 8 April 1871 |
| Birth Place: | Manchester, Lancashire, England |
| Death Place: | Fylde, Lancashire, England |
| Nationality: | British |
| Spouse: | Lilian Mary Flanagan (nee Ashley) |
| Party: | Conservative and Unionist Party |
| Children: | Reginald William Ashley Flanagan Kathleen Flanagan Lilian Myra Flanagan |
| Occupation: | Wadding and wool merchant |
William Henry Flanagan (8 April 1871 – 21 June 1944) was a British wadding and wool merchant and a Conservative and Unionist Party politician. He was the member of parliament (MP) for Manchester Clayton twice, from 1922 to 1923 and from 1931 to 1935.
Flanagan was born in Manchester on 8 April 1871, the son of Willian and Emma Flanagan. His father was a wadding manufacturer and Flanagan, who started as an apprentice, followed his father into the wadding business. He married Lilian Mary Ashley in 1899.
On 15 January 1922 Edward Hopkinson, Member of Parliament for Manchester Clayton, died and Flanagan was adopted as Coalition Unionist candidate for the resulting by-election. Flanagan is described as the managing director of the Imperial Patent Wadding Company Limited.
Flanagan was beaten in the by-election by John Edward Sutton, a trade union official and Labour candidate. Flanagan had 11,038 votes to Sutton's 14,662. Within a few months, on 15 November 1922, a general election was called and this time Flanagan beat Sutton and was elected as member of parliament for Manchester Clayton. In December 1923, a further general election was held resulting in a win for Sutton.
It was not until the 1931 general election that Flanagan won the seat again and return to Parliament. He held the seat until the 1935 general election when he decided not stand because of ill-health.
Flanagan died on 21 June 1944.