The 26-year-old has become the Magpies' eighth signing of the summer.
Newcastle United manager Rafael Benitez has spoken out about the signing of defender Ciaran Clark, telling the club's official website that it was the 26-year-old's versatility and experience that was so appealing.
Clark has become the Magpies' eighth signing of the summer after signing a five-year deal to complete a move worth around £5 million after the club activated a clause in his Aston Villa contract.
The Republic of Ireland international's move ends a 16-year association with Villa, whom he joined at the age of 11, and becomes the latest man to sign on for Benitez's revolution at St. James' Park.
Though he was seldom an undisputed regular in Villa's starting XI, Clark leaves Birmingham having racked up over 150 competitive senior appearances for the club.
He is a central defender by trade, but has also been known to play at left-back and in a defensive midfield role for Villa, an Benitez admitted that it is this versatility and experience of English football which made him such an attractive target.
Benitez told Newcastle's website: "Ciaran is a very versatile player, as a left-footed centre-back he can also play left-back and also as a defensive midfielder.
"He has a lot of experience of English football and will add good balance and competition to our squad. I am sure he will progress with us here at Newcastle, we are very happy for him to join us."
Clark becomes the latest defensive addition to Benitez's squad this summer, following Blackburn Rovers captain Grant Hanley, Atletico Madrid man Jesus Gamez, young Celtic defender Stuart Findlay, and Arsenal defensive midfielder Isaac Hayden in signing.
With Clark, Hanley, Findlay, Chancel Mbemba, Jamaal Lascelles, and Kevin Mbabu all competing for two central defensive spots, Clark will know he has a fight on his hands to establish himself as a first choice on Tyneside.