Director of football Joe Kinnear said: "We are delighted to bring Luuk de Jong to the club.
"He has an excellent pedigree and will add significantly to our striking options.
"We have been watching him for a little while now and I am sure he will prove to be a valuable acquisition for us.
"He's a great character and a proven goalscorer who I know is very keen to replicate the prolific form he showed for FC Twente in the Eredivisie."