Ivar Aavatsmark (11 December 1864 – 1 July 1947) was a Norwegian officer and politician for the Liberal Party. He finished his military career in 1928, as Major General, head of the 2nd Division and Commander of Akershus Fortress. As a politician he was a five-term MP between 1907 and 1921, and served as Minister of Defence from 1919 to 1920 and 1921 to 1923.
He was born at Aavatsmark in Høylandet as a son of farmers Anders Pedersen Aavatsmark (1820–1906) and Margrethe Salomonsdatter Mørkved (1821–1902). He was an uncle of the forester Ivar Aavatsmark and a first cousin of Ole Severin Aavatsmark and brother-in-law of Høylandet mayor Lorents Mørkved.
In November 1898 in Helsinki he married the singer Ida Emilia Basilier Flodin (1870–1957). She was a daughter of politician Frithiof Ferdinand Flodin and sister of Ida Basilier-Magelssen.
He attended school in Namsos before finishing his secondary education at Trondhjem Cathedral School in 1886. He then took officer training at the Norwegian Military Academy, which he finished in 1889. He was promoted to Premier Lieutenant in 1890 and graduated from the Norwegian Military College in 1892. After one year in the King's Guard he was an aspirant in the general staff from 1894 to 1898. He was then promoted to Captain, and after a period as an adjoint from 1900 to 1903 he was a teacher at the Norwegian Military College from 1903 to 1911. Following the death of his older brother he took over the family farm in Høylandet in 1904, and resided there from 1906 to 1911.