Kullervo Achilles Manner (12 October 1880 in Kokemäki, Finland – 15 January 1939 in Ukhta-Pechora, the USSR) was a Finnish journalist and politician, and later a Soviet politician. He was a member of the Finnish parliament, serving as its Speaker in 1917. He was also chairman of the Social Democratic Party of Finland between 1917–1918. During the Finnish Civil War, he led the Finnish People's Delegation, a leftist alternative to the established Finnish government. After the war, he escaped to the Soviet Union, where he co-founded the Finnish Communist Party.
Manner was born a priest's son in Kokemäki. His father Gustaf Manner worked in various parishes, including those of Lappi and Vampula. After graduating from high school in 1900, Manner worked as a journalist in Porvoo and later in Helsinki. In 1911, Manner received a prison sentence for lèse majesté (a lesser crime similar to treason) against Nicholas II. He was elected to the Finnish Parliament as a Social Democrat from Uusimaa in 1910 and 1917. He was appointed Speaker of the Parliament in 1917. Manner's brother Arvo was governor of Viipuri and Kymi provinces from the 1920s to the 1950s.