Kazuki Matsunaga is a Japanese male voice actor affiliated with the agency EARLY WING. He was born on January 16, 1995, in Ibaraki Prefecture, Japan. He stands 161 cm tall and has O-type blood.

Matsunaga's path to voice acting was influenced by a personal realization. During his middle and high school years, he was a member of his school's badminton club. After graduating from high school, he attended a vocational school for voice actors for two years before joining WAHO Academy, the training school affiliated with EARLY WING. A significant moment that steered him toward a career using his voice came after watching a television program. He had a dream in which he completely lost his hearing and could not hear even his own voice. This dream profoundly changed his perspective, making him appreciate the ability to speak and inspiring him to pursue a profession that utilized his voice.

He made his debut in the entertainment industry in 2017, providing voices for the digital comic A Regulation of Kiss. His first regular role in a television anime came in the spring of 2018 when he was cast as Tanishi in the short-form anime series Crossing Time. This series, which depicts various conversations and vignettes that occur while people wait at a railroad crossing, marked his professional anime debut. His role as Tanishi is one of his most recognized performances.

Beyond this debut role, Matsunaga's career has included work in other media. He has contributed voices to several video games, including roles such as Drew in Thousand Memories, a character in A3!, and Ranhoshi (Mori Ranmaru) in Sengoku Taiga. He has also worked on dubbing for animation, providing the voice for a character named Pado in the 2021 series Duda & Dada: The Animal Adventure. In addition to voice work, Matsunaga has appeared in stage productions and live reading events, demonstrating his versatility as a performer. His stage credits include roles in plays such as Ayumi in 2019, the reading drama Gakuen Death Panel 2020, and Yoshamaru in Youkai Senki Odorokei in 2023.

Matsunaga has listed stage combat and traditional Japanese dance as his specialties and hobbies. He has also expressed an interest in working in a capacity that involves dancing, beyond his voice acting career. His other hobbies include online shopping and cooking; at one point, he even considered training to become a pastry chef. He is known to be good friends with a fellow voice actor from his agency, Matsuoka Ippei.