The 19 year-old defender has joined Newcastle today from Serbia's FK Jedinstvo Ub.
Pivas told the club's website: “It’s absolutely unbelievable to join such a big club like Newcastle United and I cannot wait to get started. I see the project of the club and it looks great which helped convince me to sign for Newcastle.
“I see the young players have developed very well here and I would like to do the same - to develop and get into Newcastle's first-team. I’m very excited and I can’t wait to begin."
He added: “My best strengths are my pace, being a centre-back, as well as my heading and passing ability.
“I want to start playing for the first-team as soon as possible and show what I can do. I’ve watched a lot of Newcastle's games, they are playing very well and I believe I can play at that level.
“I won promotion last season and it was amazing, getting to the top tier in Serbia. It was an incredible feeling and I learnt a lot playing as a centre-back because of my manager (Ivan Radovanović), who played in Serie A for 15 years and was quite important to me."