<P> Nancy Jean Cartwright ( born October 25 , 1957 ) is an American actress , voice actress and comedian , known for her long - running role as Bart Simpson on the animated television series The Simpsons . Cartwright also voices other characters for the show , including Nelson Muntz , Ralph Wiggum , Todd Flanders , Kearney and Database . </P>
who does the voice of nelson on simpsons
Nancy Jean Cartwright