July 7 – The United States, Russia, the United Kingdom and Japan, meeting in Washington, D.C., sign the North Pacific Fur Seal Convention of 1911, prohibiting open-water seal hunting of the endangered fur seal in the North Pacific Ocean, the first international treaty to address wildlife conservation issues. In the next six years, the seal population increases by 30%.
Robert Remak's doctoral dissertation Über die Zerlegung der endlichen Gruppen in indirekte unzerlegbare Faktoren establishes that any two decompositions of a finite group into a direct product are related by a central automorphism.
Traian Lalescu publishes Introduction to the Theory of Integral Equations, the first ever monograph on the subject of integral equations.
June 24–30 – Domenico Pacini runs a series of measurements of underwater ionization in the Gulf of Genoa, demonstrating that the radiation later recognised as cosmic rays cannot be originated by the Earth's crust.
November 4 – MS Selandia, the first large ocean-going diesel ship, is launched in Denmark; Ivar Knudsen is the diesel engineer. The 1909-launched Dutch diesel tankerVulcanus also enters service this year.
^Ponzo, M. (1911). "Intorno ad alcune illusioni nel campo delle sensazioni tattili sull'illusione di Aristotele e fenomeni analoghi". Archives Italiennes de Biologie.
^Skennerton, Ian (2001). Small Arms Identification Series No. 14: .303 Lewis Machine Gun. Gold Coast, QLD (Australia): Arms & Militaria Press. p. 5. ISBN0-949749-42-7.