Kōji Kikkawa (吉川晃司, Kikkawa Kōji, born August 18, 1965) is a Japanese singer, musician and actor. His most recent album is 2022's Over the Nine.

Kōji was born in Hiroshima and his music career began on February 1, 1984, with "Monica" (later remade in Cantonese sung by Leslie Cheung) and he won eight music awards in the same year. After taking a short break in 1988, he came back as a lead singer in the band Complex with Tomoyasu Hotei (former guitarist of Boøwy) and "Be My Baby" was released. Complex remained as one of the most popular bands in Japan until 1990, when it was announced that Complex had disbanded.

After "Complex", Kōji released series of hit singles such as "Setsunasa O Korosenai", "Kiss Ni Utarete Nemuritai" and "Boy's Life". Kōji completed a "20th Anniversary Tour" at Budokan on February 1, 2005.

In 2006 he recorded "One World," the theme for the 2006 motion picture Kamen Rider Kabuto: God Speed Love. More recently, he had teamed up with popular Japanese DJ TWINS to release a single "Juicy Jungle". Also, DJ TWINS had released an album with remixes of several of Kōji's previous hits.

With this new sound-disco revisit, Kōji redefined himself like he does year after year. Throughout all his career, it could be considered that Kōji had outgrown from an idol to an artiste that explore the music boundary. He writes his own songs, produced and arranged his own albums and also played most of the instruments in it. He had just released a remix album of his old hits-titled-DISCO K2. In April 2007, a new single "BABY JANE" was released.

In 2011, Kōji and Tomoyasu Hotei reunited as Complex for two concerts at the Tokyo Dome to benefit victims of the Tohoku earthquake and tsunami. The duo had not performed together as Complex for almost 21 years.

In 2024, 13 years later, Kikkawa and Hotei reunited again for another Complex benefit concert at the Tokyo Dome, this time to benefit the victims of the 2024 Noto earthquake.

He portrays Sokichi Narumi/Kamen Rider Skull for the Kamen Rider W franchise, and sung "Nobody's Perfect," Skull's theme.