The 24-year-old has signed a long-term contract with the Magpies for an initial fee of £39m, with a further £4m in add-ons.
Ramsey made 167 appearances for Aston Villa, including 10 in last season's Champions League, and was part of England's European Under-21 Championship-winning squad in 2023.
Newcastle manager Eddie Howe praised Ramsey as a fantastic addition, highlighting his versatility and directness in attack.
Ramsey expressed his delight at the move, stating he is excited to get started and believes his game will suit Newcastle's energetic style.