Denis McDonnell (c.1818-2 February 1866) was a local politician active in the Clerkenwell area. A Radical in politics, he was appointed a member of the committee to secure the re-election of Thomas Slingsby Duncombe as MP for Finsbury in 1859. During the American Civil War McDonnell was treasurer of London Emancipation Committee which sought to free the slaves. Resident at 65 Pentonville Road, he was elected to Clerkenwell Vestry, and was the parish's representative on the Metropolitan Board of Works from 1861 until his death.