The Nobel Prize in Physiology or Medicine 1919 was awarded to Jules Bordet "for his discoveries relating to immunity".

Jules Bordet received his Nobel Prize one year later, in 1920. During the selection process in 1919, the Nobel Committee for Physiology or Medicine decided that none of the year's nominations met the criteria as outlined in the will of Alfred Nobel. According to the Nobel Foundation's statutes, the Nobel Prize can in such a case be reserved until the following year, and this statute was then applied. Jules Bordet therefore received his Nobel Prize for 1919 one year later, in 1920.