Forest owner Evangelos Marinakis said: "Morgan is a special player – not just in terms of talent, but character and mentality. He represents everything we want this football club to be: he is a winner, talented, ambitious, fearless, and proud.
"There was significant interest from various clubs, but we were determined to build our future with Morgan at the heart of it. I promised our fans we would not only compete, but grow stronger and stronger every season. Today is another big step in that journey."