William Franklin Chapin (22 May 1831 – 14 November 1885) was an American politician who served as the first Mayor of Lincoln, Nebraska as a member of the Republican party from 4 April 1871 to 10 April 1872 as well as serving in the Nebraska Legislature, including being its speaker.

During this time, Chapin was working as a farmer, a teacher in Lexington and a lawyer after he was admitted to the bar of Nebraska in 1857.

Ultimately he baceme the Speaker of Nebraska Territory House of Representatives in 1866, serving until 1869 when he retired from the Legislature.

He served in this position until 10 April 1872, when he ran for the Republican nomination for the 1872 Nebraska gubernatorial election, losing the primary to Robert Wilkinson Furnas by a few votes.

Chapin retired from politics following his primary loss and died in Grand Island, Nebraska on 14 November 1885, aged 54.