Ospreys Director of Rugby Kevin Hopkins, commented: "We are delighted to have secured another of our young key players on a long term contract.
"James is a player of massive potential and this is becoming more and more evident with each match he plays for Wales and the Ospreys. It is great news for both Wales and our region that he is staying with the Ospreys.
"James hails from Port Talbot, he has come through the ranks in our region and it is vital to our success that players such as James stay within our environment if he is to achieve his full potential. This is another key step towards us achieving our ambitions, both domestically and in cross-border competitions over the coming seasons."
Hook commented: "I am delighted to have re-signed with the Ospreys. This region is going to have massive success over the next few years and I want to be a part of it.
"I have grown up in the area, the Ospreys are my local professional side and I just could not imagine going anywhere else. We have facilities and a growing fan base that will rival any European side and this makes it a great time to be a player at this region."