The 2004 British Superbike season was the 17th British Superbike Championship season. Shane Bryne was the reigning champion but he left the race in MotoGP.
John Reynolds took his third and final championship for Rizla Suzuki after starting the season with a run of 11 consecutive podium finishes. Michael Rutter, riding for HM Plant Honda, also started the season strong, but a mid-season slump saw him finish 29 points behind in 2nd. Reynolds' team mate, Yukio Kagayama finished the season 3rd.
The Superbike Cup for Privateer entries was dominated by James Ellison who finished 133 points clear of nearest challenger Jon Kirkham.