According to Official Guinness Records,
The longest contract in NHL ice hockey is 15 years, originally signed by Rick DiPietro (USA) with the New York Islanders on 12 September 2006 and later matched by Ilya Kovalchuk (Russia) with the New Jersey Devils on 3 September 2010. DiPietro's contract paid $67.5 million (£43 million), while Kovalchuk's is for $100 million (£63.7 million).
For a complete list of 2010 records, please visit 2010 Guinness Records in United States.