Dmitri Iosifovich Ivanovsky (alternative spelling Dmitrii or Dmitry Iwanowski; Russian: Дми ́ трийИо ́ сифо ви чИв ано ́ вск ий; 28 October 1864–20 June 1920) was a Russian botanist, the co-discoverer of viruses (1892) and one of the founders of virology.