The 24-year-old French striker has signed a "long-term contract" with the Magpies and arrives on Tyneside for an undisclosed fee.
"I'm very happy to be here at Newcastle," said Riviere. "When the club spoke to me I said yes immediately. It was an easy decision because Newcastle is a big club with great fans and a good stadium.
"My dream was always to play in the Premier League and Newcastle have given me the opportunity to realise that."