Robert "Big Mojo" Elem (January 22, 1928 – February 5, 1997) was an American Chicago blues bass guitarist and singer. Although he recorded only one studio album in his long career, Elem was a part of the Chicago blues scene for over forty years. He variously backed Arthur "Big Boy" Spires, Lester Davenport, Freddie King, Magic Sam, Junior Wells, Shakey Jake Harris, Jimmy Dawkins, Luther Allison, and Otis Rush.
He was noted as a "born entertainer whose joking and acting on stage appeal to club audiences". Elem's energetic on-stage persona underpinned his lengthy performing career.