William Harris was a Liberal politician and strategist in Birmingham, England, in an era of dramatic municipal reform. On his death, he was described by one obituary-writer as "one of the founders of modern Birmingham". J. L. Garvin called him "the Abbé Sieyès of Birmingham" ; and Asa Briggs "a most active and intelligent wire-puller behind the scenes". He was dubbed the "father of the Caucus", the highly organised and controversial Liberal party machine that had its origins in Birmingham, but was afterwards introduced at national level to the National Liberal Federation. He served as the first Chairman of the National Liberal Federation from 1877 to 1882. By profession he was an architect and surveyor; and he was also a prolific journalist and author.

A caucus is a meeting or grouping of supporters or members of a specific political party or movement. The exact definition varies between different countries and political cultures.