The 20-year-old put pen to paper on a five-year deal for an undisclosed fee, understood to amount to around £5million, after flying into Tyneside for a medical yesterday morning.
Pardew said: "We are delighted to bring to Davide to Newcastle. "He is a quality left-back and an established international who also gives us flexibility in defence.
"Davide is a young lad and a great signing for us and I am sure he will adapt to the Premier League very quickly."
Santon, who can play in both full-back positions, made 40 appearances for Inter after emerging from the ranks, and is relishing the chance to test himself in the Barclays Premier League.
He said: "I am really pleased to sign for Newcastle. The chance to play in the Premier League and in front of 50,000 fans at St. James' Park was too good to turn down.
"This is an ambitious club who want to move forward and I want to help them achieve that."
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