Los Angeles's successful bid was led by Casey Wasserman, the Los Angeles businessman who is also chairman of the city's bid for the 2024 Olympics.
"We are honoured that the NFL is bringing the Super Bowl to Los Angeles in 2021," Wasserman said in a statement, which paid tribute to Rams owner Stan Kroenke's investment in the team's new stadium.
"Stan Kroenke's vision for the Rams stadium and the surrounding campus makes Inglewood an ideal venue for staging the Super Bowl of the future, and we look forward to inviting the nation and the world to LA for a historic fan experience."
Atlanta will host Super Bowl LIII in 2019 while Miami will stage Super Bowl LIV in 2020. The 2019 Super Bowl will take place in a $1.5 billion stadium that the Atlanta Falcons will move into in 2017.
New Orleans and Tampa were among the unsuccessful bidders who had been hoping to land the Super Bowl.
Next year's event will take place in Houston while in 2018 Super Bowl LII will be played in the Minnesota Vikings new stadium.