Ivar Johannes Alnæs (October 5, 1868 – April 2, 1956) was a Norwegian teacher and linguist. Alnæs was born in Fredrikstad, the son of the school principal Jørgen Lauritz Alnæs and Elise Martine Hansen. He was the brother of the composer Eyvind Alnæs. He enrolled in university studies in 1887 and received a candidatus magisterii in 1894. He was an adjunct instructor and senior instructor at the Hammersborg Elementary School in Oslo from 1902 to 1917. From 1918 to 1937 he was the chancellor of . He also taught at the University of Oslo from 1918 onward.