Kōji Tamaki (玉置 浩二, Tamaki Kōji, born September 13, 1958) is a Japanese singer-songwriter and actor. He has been well known as frontman of the rock band Anzen Chitai that debuted in 1982 and enjoyed a successful career, particularly during the 1980s. In the 1990s, he also began his career as a solo artist. He is widely regarded as one of the greatest Japanese vocalists.

In 2014, he was ranked first by a panel of 200 experts for the best ever singing voice in Japan. Moreover, in 2021 Koji was voted as the greatest active male Japanese singer, with 190 experts agreeing that he is a "living national treasure of music" and that he portrays an "unparalleled mass of expressiveness and emotion which only seems to get better with age".

As a vocalist and a songwriter of the band, Tamaki spawned multiple successful compositions which were mostly co-written by lyricists including Gorō Matsui and Yōsui Inoue, by the time that the group suspended their career in 1993.

In 1987, Tamaki released the first solo single "All I Do", and continued his solo career after Anzen Chitai went into hiatus (1993–2001, 2004–2009). Throughout his solo career, he has released 23 singles and over a dozen studio albums. His song "Den-En" released as a single in 1996 became a massive hit, which reached the number-two on the Japanese Oricon charts and sold in excess of 900,000 copies.

Tamaki has also been known as an actor who has appeared in seven feature films and numerous television dramas. He has started acting career for the first time on "Prussian Blue no Shozo", the 1986 motion picture he starred.

Anzen Chitai returned from a recess and released their new single "Aoi Bara/Wine Red no Kokoro (2010 version)" on March 3, 2010.

On his 2012 album Offer Music Box, Tamaki — who composed the original song — covered Yuki Saito's song "Kanashimi yo Konnichi wa", which was used as the first theme song for the anime television series Maison Ikkoku.