Toshitada Doi (土井 利忠, Doi Toshitada, born February 2, 1943) is a Japanese electrical engineer, who played a significant role in the digital audio revolution. He received a degree in electrical engineering from the Tokyo Institute of Technology in 1964, and a PhD from Tohoku University in 1972.He joined Sony Japan in 1964 and started the first digital audio project within Sony.