Janis or Janiš is a surname. Notable people with the surname include:
Byron Janis (born 1928), American concert pianist (no relation to Conrad Janis)
Conrad Janis (1928–2022), American actor and jazz musician (no relation to Byron Janis)
Dorothy Janis (1912–2010), American silent film actress
Elsie Janis (1889–1956), American musical theatre and vaudeville performer
Irving Janis (1918–1990), social psychologist who pioneered the groupthink theory
Jaroslav Janiš (born 1983), Czech auto racing driver
Josef Antonín Janiš (1749–1821), Czech priest and apiculturist
Linzie Janis (born 1979), American television journalist
Sidney Janis, (1896–1989), American art dealer, collector, and writer