Ralph Peterson, Jr. (b. May 20, 1962, Pleasantville, New Jersey) is an American jazz drummer and bandleader.
Four of Peterson's uncles and his grandfather were all drummers, and Peterson himself began on percussion at age three. He was raised in Atlantic City, where he played trumpet in high school and worked locally in funk groups. He applied to Livingston College, Rutgers, for drums but failed the percussion entrance exam, and enrolled as a trumpeter instead. In 1983, he joined Art Blakey's Jazz messengers as the second drummer, playing with him for several years. He worked with Terence Blanchard and Donald Harrison in 1984, and with Walter Davis (1985, 1989), Tom Harrell (1985), Out of the Blue (1985–88), Branford Marsalis (1986), David Murray, Craig Harris (1987), James Spaulding (1988), Roy Hargrove (1989), Jon Faddis (1989), Dewey Redman and Mark Helias (1989), and Wynton Marsalis (with the Count Basie ghost band).
In the 1990s, Peterson played as a sideman with Jack Walrath, Craig Handy, Charles Lloyd, Kip Hanrahan (1992), Bheki Mseleku, Courtney Pine, Steve Coleman, George Colligan, Stanley Cowell, Mark Shim, and Betty Carter. He began recording as a leader around 1988, with a quintet V, or Volition, with Terence Blanchard, Steve Wilson, Geri Allen, and Phil Bowler. He also worked with Allen and Bowler as a trio in Triangular; Essiet Essiet replaced Bowler for their 1988 recording. In 1989 he recorded in quartet format as Fo'tet, with Don Byron, Steve Wilson (later Bobby Franchesini), Melissa Slocum (later Belden Bullock), and Bryan Carrott. After living in Canada for some time he returned to Philadelphia, where he worked further with Fo'Tet and also recorded as Triangular Too with Slocum and Uri Caine. He also led a group Hip Pocket, with whom he played trumpet.
Peterson has taught at Philadelphia's University of the Arts.