Sir John Williams Benn, 1st Baronet (November 13, 1850-10 April 1922) was a British politician, particularly associated with London politics, and noted as the grandfather of Tony Benn.

Benn was born in Manchester but his parents moved the family to east London the following year, where they opened an institute for homeless boys. Benn was largely taught at home and at the age of 17 joined a furniture company. He later (1880) established a trade journal, The Cabinet Maker, which eventually became the furniture trade's leading publication (when politics became his main interest, the family's publishing business were taken over by his eldest son Ernest Benn (1875-1954)).

When the London County Council was established in January 1889, Benn accepted an invitation to stand as a Progressive Party candidate for East Finsbury and was elected. Like his contemporary Will Crooks, Benn was active in the 1889 London docks strike, and, as an increasingly prominent local politician, was invited to stand for Parliament in 1891 as the Liberal Party candidate for Wapping.

He was later narrowly defeated at the General Election in 1895 but he concentrated on his continuing work as a London councillor, helping introduce electric trams to London's streets in 1903. A year later, he returned to Parliament after winning a by-election at Devonport, a seat he retained until defeated in 1910. In the meantime his son, 28-year-old William Wedgwood Benn, had also been elected to Parliament, winning Benn's former seat at Wapping in 1906.

Knighted in 1906 and created a baronet in 1914, John Benn remained a member of the London County Council until his death in 1922, leading the Progressive Party until ill health forced him to relinquish that role in 1918.