Edvard Armas Järnefelt (August 14, 1869 – June 23, 1958), was a Finnish conductor and composer, who achieved some minor success with his orchestral works Berceuse and Praeludium. He spent much of his conducting career at the Royal Swedish Opera in , Sweden.
Armas Järnefelt was born in Vyborg, in the Grand Duchy of Finland, the son of General August Aleksander Järnefelt and Elisabeth Järnefelt (née Clodt von Jürgensburg).
Järnefelt studied with Ferruccio Busoni in Helsinki and with Jules Massenet in Paris. Both Järnefelt and Busoni enjoyed a close relationship with Jean Sibelius, who was married to Järnefelt's sister Aino. From 1905 Järnefelt had a long career as conductor at the Royal Swedish Opera in , beginning as repetiteur from 1905-1911 (he became a Swedish citizen in 1909); conductor 1911-1923 and chief conductor 1923-1933.
Between 1932-36 Järnefelt was the artistic director and conductor of the Finnish National Opera. He presented, among others, Siegfried and Götterdämmerung from Wagner's Ring cycle, and Parsifal. He was principal conductor of the Helsinki Philharmonic Orchestra 1942–1943, and also returned to the Royal Swedish Opera as chief conductor from 1938 to 1946. He died in .