McWilliams was part of Villa's Under-18 team that achieved a remarkable triple win in the FA Youth Cup, Premier League South, and Premier League National Final.
Mark Harrison, the head of Aston Villa's academy, expressed his delight at McWilliams' new contract.
"Ashton has been with us since he was nine years old, so it's great to see him take this important step in his football career," Harrison said.
McWilliams is known for his aggressive playing style as a full-back, always looking to get forward and support his team's attacks.
He also demonstrated his leadership skills by captaining the Under-18 team during their successful season.
The club is excited to see McWilliams continue to grow and develop as a player.