Mason joined Doncaster on loan last summer and made 38 League Two appearances to help Rovers to automatic promotion.
And now the 20-year-old defender, who failed to make a single senior outing for Aston Villa, has moved to the Keepmoat on a two-year deal.
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Niall Mason helped Doncaster to promotion to League One
Niall Mason has joined Doncaster Rovers on a permanent deal
Aston Villa
An Aston Villa statement read: "Niall Mason has joined Doncaster Rovers on a permanent deal.
"The versatile defender spent the 2016/17 campaign on loan at the Keepmoat and has now penned a two-year contract."
On his summer move, Mason said: "I had a couple of options to go a bit higher up the pyramid, but this is a great platform for me.
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Niall Mason failed to make a single first-team appearance for Aston Villa
"I am working with a manager and coaching staff who know my game inside out and can get the best out of me.
"They've all been really good to me and helped me develop, they're probably the best coaching staff in League Two. They are only going to help me progress as a player."
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