Shinya Niiro is a Japanese actor born on April 21, 1975, in Kobe, Hyogo Prefecture, Japan. His career began when he was scouted as a model at the age of 16. After a brief period studying at the Osaka University of Arts, he moved to Tokyo at the age of 20. He began performing on stage in 1994 and for two years starting in 1997, he appeared as an "utano oniisan" (song big brother) on the NHK-BS2 children's program Nikoniko Punk ga Yatte Kita.

Niiro has a substantial background in musical theatre. In 2000, he performed as the first Todt Tänzer (Black Angel) in the Japanese production of the musical Elisabeth. In 2002, he played the lead role of Jesus in a rock musical production of Godspell. He initially performed under the stage name NIRO but changed to his real name, Shinya Niiro, in December 2003. He is associated with the talent agency Watanabe Entertainment.

For audiences familiar with anime and manga adaptations, Niiro is known for his role in the live-action film of Cells at Work! (Hataraku Saibō), where he portrays the pathogenic bacterium Streptococcus pyogenes. It was confirmed that the film would have IMAX and 4D screenings in Japan before its theatrical release on December 13, 2024, and later became available globally on Netflix in June 2025.

Beyond this role, his acting credits include a significant part in the tokusatsu genre. He had a regular role as King in the 2008 television series Kamen Rider Kiva. His filmography also includes appearances in several live-action television dramas. He played Toyotomi Hidetsugu in the 2016 NHK Taiga drama Sanada Maru and has had roles in other series such as Totto-chan! (2017) and M: Ai Subeki Hito ga Ite (2020). He has also appeared in the historical drama Seiten wo Tsuke (2021) and Kamakura-dono no 13-nin (2022). In addition to his on-screen work, he has continued to be involved in Straight Plays, including performances in the productions OZ (2005) and Talk Like Singing (2009).