Elanga told Newcastle's website: "I'm excited, I'm really happy but most importantly I'm ready. I'm ready to put on this black and white top to really fight for this team and give everything for the passionate fanbase that lives and breathes football.
"I had an amazing two years at Nottingham Forest, they really helped me to become the player I am today, but I'm really happy to be here now. The club won a trophy last season and are building something unique, something special that I really want to be part of.
"I really want to buy into the culture, into the DNA of this club. I'm really happy to be here and I can't wait to get started."