Yōichi Masukawa is a Japanese voice actor born on December 27, 1978, in Kanagawa Prefecture, Japan. He stands 175.5 cm tall and has A-type blood. Masukawa began his voice acting career in 1999 and has since become best known for his long-standing role as Rock Lee in the Naruto anime franchise.

Masukawa made his professional debut in 1999, providing the voice for the character Sibuxiang in the anime series Soul Hunter. He remained active throughout the 2000s, taking on supporting roles in a variety of anime titles. His early career includes the role of Franz in The Galaxy Railways in 2003, Haruhiko Uchiyama in The Gokusen in 2004, and Tamehiko Kawano in Desert Punk in the same year. He also appeared as Shu Akitsu in the supernatural series Kekkaishi in 2006 and had a guest role in an episode of Detective Conan.

His career-defining role began in 2002 when he was cast as Rock Lee, the energetic and hardworking ninja from the Hidden Leaf Village, in the original Naruto anime series. He continued to voice this character for over a decade and a half, portraying Rock Lee across numerous installments of the franchise. His work as Lee includes the sequel series Naruto Shippūden, the spin-off series Naruto Spin-Off: Rock Lee & His Ninja Pals, and the sequel Boruto: Naruto Next Generations. He also voiced the character in multiple theatrical films, such as Naruto the Movie: Guardians of the Crescent Moon Kingdom, Naruto Shippūden: The Will of Fire, Road to Ninja: Naruto the Movie, Naruto Shippūden: Blood Prison, and Boruto: Naruto the Movie. Beyond television and film, he has also voiced Rock Lee in various video games based on the Naruto franchise.

Throughout his career, Masukawa has been affiliated with several talent management agencies. He was initially represented by Genki Project before moving to Ken Production. He later joined Production Ace, where he remained from April 2012 until the end of August 2015. Following his time with Production Ace, he transitioned to working as a freelance voice actor. In addition to his voice work, Masukawa has also taken on work as a stage director, becoming active in this role around 2014.