John Michael O'Keefe (19 January 1935 – 6 October 1978) was an Australian rock and roll singer whose career began in the early 1950s. A pioneer of Rock music in Australia, his hits include "Wild One" (1958), "Shout!" and "She's My Baby". Often referred to by his initials "J.O'K." or by his nickname "The Wild One", O'Keefe was the first Australian rock n' roll performer to tour the United States, and the first Australian artist to make the local Top 40 charts. He had twenty-nine Top 40 hits in Australia between 1958 and 1973. In his twenty-year career, O'Keefe released over 50 singles, 50 EPs and 100 albums. O'Keefe was also a radio and television entertainer and presenter.

O'Keefe died in 1978 from a drug overdose. He was the younger brother of Australian jurist Barry O'Keefe (a former head of the New South Wales ICAC). His father, Alderman Ray O'Keefe, was Mayor of Waverley Council in the early 1960s. Through Barry, O'Keefe was the uncle of Australian television personality Andrew O'Keefe.