Tamotsu Nishiwaki is a Japanese voice actor born on September 21, affiliated with the talent management firm Aoni Production. He is a native of Osaka Prefecture. His career spans numerous anime television series, original video animations, and video games, often voicing supporting characters.

Nishiwaki's filmography includes a wide range of roles in long-running and popular series. He has appeared in One Piece, where he voiced the character Nezumi (also known as Mouse) and other roles such as a cook and pirates. In the anime adaptation of Gin Tama, he provided the voice for the character Kusano Yoshihito. His other television credits include roles in AIR, the fifth installment of GeGeGe no Kitaro, and Sgt. Frog. In 2016, he appeared in an episode of Case Closed (Detective Conan) as Haruki Toriumi. More recently, he is confirmed to voice a character in the 2021 short-form anime ABCiee Working Diary, where he plays the role of Koi-san. His work also extends to tokusatsu productions; he is credited with voicing Ura in an episode of the Super Sentai series.

In addition to his television work, Nishiwaki has participated in original video animations such as Freedom-Project and Shin Getter Robo vs. Neo Getter Robo. His film credits include a part in the animated feature Steam Boy and the 2013 compilation film One Piece: Episode of Nami. He has also contributed to audio dramas and CDs, including the VitaminX × Sheep's Sleep series.