John Michael O'Keefe, known as Johnny O'Keefe (19 January 1935 – 6 October 1978) was an Australian rock and roll singer whose career began in the 1950s. Some of his hits include "Wild One" (1958), "Shout!" and "She's My Baby". In his twenty-year career, O'Keefe released over 50 singles, 50 EP's and 100 albums.

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, and he remains Australia's most successful chart performer, with twenty-nine Top 40 hits to his credit in Australia between 1959 and 1974.

Johnny O'Keefe was the younger brother of Australian jurist Barry O'Keefe (a former head of the New South Wales ICAC) and the uncle of comedian and TV presenter Andrew O'Keefe. His father Alderman Ray O'Keefe was Mayor of Waverley Council in the early 1960s

'She's My Baby' was added to the National Film and Sound Archive's Sounds of Australia Registry in 2007.