John Dillon (1851-1927) was an Irish nationalist. A supporter of Charles Stewart Parnell, he entered Parliament in 1880 and was arrested several times for his advocacy of boycotting and agrarian agitation. After the Parnell divorce scandal, Dillon led the anti-Parnell faction until the Nationalist party was reunited (1900) under the leadership of John Redmond.
During World War 1, Dillon incurred the enmity of Sinn Fein by encouraging military recruiting in Ireland in spite of his opposition to conscription. He succeeded (1918) Redmond in the leadership of the Nationalist party, but his career came to an end after the Sinn Féin victory in the 1918 election.