The 2004 Formula Nippon Championship was the thirty-second season of premier Japanese single-seater racing, and the ninth under the Formula Nippon moniker. Eight teams and 17 drivers competed in the series.
The series was contested over nine rounds at five venues. Fuji Speedway was closed for 2004 due to renovations, and for the first time, the series raced outside of Japan as Sepang International Circuit in Malaysia was added to the calendar.
Dandelion Racing driver Richard Lyons won his first series championship, defeating André Lotterer after scoring more points in the final race of the season, which was the championship tiebreaker. Lyons became the third driver to win the Formula Nippon and All-Japan Grand Touring Car GT500 Championships in the same year.
All teams used tyres supplied by Bridgestone, Lola B03/51 chassis, and Mugen MF308 engines.