Järnefelt is a surname originating in Sweden and Finland. Notable people with the surname include:
Aino Sibelius (née Järnefelt; 1871–1969), Finnish wife of composer Jean SibeliusAlexander Järnefelt (1833–1896), Finnish general, political figure, and topographerArmas Järnefelt (1869–1958), Finnish composer and conductorArvid Järnefelt (1861–1932), Finnish judge and writerEero Järnefelt (1863–1937), Finnish realist painterElisabeth Järnefelt (1839–1929), “mother of Finnish art and culture”Gustaf Järnefelt (1901–1989), Finnish astronomer