Masato Hagiwara is a Japanese actor and voice actor born on August 21, 1971, in Kanagawa Prefecture. He began his entertainment career in 1987 with a minor role in the television drama Abunai Deka and made his film debut in 1989. Prior to his voice acting work, he established himself as a prominent live-action film and television actor, winning the Japan Academy Prize for Best Newcomer in 1994 and receiving multiple Best Supporting Actor nominations and awards for his performances in films such as Marks no Yama and Cure.

Hagiwara entered the field of voice acting in the early 2000s. His debut anime role was as Takuya Shirakawa in the 2004 film The Place Promised in Our Early Days. He is best known for portraying intense, psychologically complex characters. This includes his performance as the titular mahjong genius in the 2005 series Akagi, a role that connected his voice acting career with his personal passion for the game. His most iconic role is Kaiji Itō in the Kaiji anime series, which began with Kaiji: Ultimate Survivor in 2007 and continued with Kaiji: Against All Rules in 2011, as well as a cameo in Mr. Tonegawa: Middle Management Blues in 2018. Other significant voice roles include Tōa Tokuchi in the baseball anime One Outs and Watashi in Kappa no Kaikata. In film, he voiced Dario Montoya in Garo: Divine Flame.

Hagiwara's career is marked by a strong association with stories about gambling and strategy, largely due to his lead roles in Akagi and Kaiji. This interest is not just professional; in 2018, he became a licensed professional riichi mahjong player with the Japan Professional Mahjong League and was drafted to play for Team Raiden in the competitive M-League, effectively blending his two careers. His deep and commanding voice has also made him a sought-after narrator for documentaries and television programs. In 2024, he took on the role of Ultraman Arc in the series of the same name, a franchise he has been a fan of since childhood. For his live-action work, he has received numerous accolades, including the Blue Ribbon Award for Best Supporting Actor and multiple Japan Academy Prize nominations.