"Dias was pivotal to Man City's third Premier League title in four years as he made an immediate impact following his move from Benfica in September 2020," the Premier League said in a statement.
"The 24-year-old fitted seamlessly into Pep Guardiola's side and emerged as a leader at the back as City went on a 15-match winning streak, the fourth-longest such run in Premier League history," it added.
The Portuguese defender scored one goal in 32 games as he helped City win the EFL Cup -- English Football League --and reach the UEFA Champions League final.
Dias beat seven other nominees to the award, including De Bruyne, Bruno Fernandes, Jack Grealish, Harry Kane, Mason Mount, Mohamed Salah, and Tomas Soucek.
Foden clinches Young Player of Season award
The 2020/21 Hublot Young Player of the Season award went to the City's Phil Foden.
"Man City midfielder voted the best player aged 23 or under at the start of 2020/21," the Premier League said.
The 21-year-old produced nine goals and five assists in 28 games.
Foden is the Blue Skies' fourth 2020/21 season awards winner.
Ruben Dias and Guardiola were voted Player and Manager of the Season, respectively, whereas Liam Delap was named PL2 Player of the Season.
