The 20-year-old German finished second on the Senators with 58 points (22 goals, 36 assists) in 79 appearances in 2021-22.
The Senators previously signed captain Brady Tkachuk, center Josh Norris, winger Drake Batherson and defenseman Thomas Chabot to long-term deals.
“Tim is a dynamic offensive player who utilizes an exceptional blend of speed and skill to be a consistent difference-maker,” Dorion said in a statement. “He’s electrifying and has quickly become a fan favorite for good reason.”
Ottawa, which has failed to make the playoffs since reaching the 2017 Eastern Conference final and has gone through a major rebuild, made news earlier this summer by acquiring forward Alex DeBrincat in a trade the Chicago Blackhawks and signing veteran forward Claude Giroux in free agency.
The Senators, who finished with 73 points last season, also traded goaltender Matt Murray to the Toronto Maple Leafs before acquiring Cam Talbot from the Minnesota Wild as his replacement.
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