The defender, who joined City as a five-year-old, will look to continue gaining experience at Championship level after making 36 appearances for West Brom during a loan spell last term.
The Manchester-born centre-half made his City debut against Chelsea in 2016 and in 2016/17 played against Steaua Bucharest and Celtic in the Champions League.
In total, he has made eight first-team appearances for City and has also represented England at youth level on 15 occasions.
Everyone at City wishes Tosin the best during his time at Blackburn.
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