Eklund is part of a trade that also sends Finnish forward Kasper Halttunen and the rights to college player Brandon Svoboda to Ottawa, which in return sends the ninth pick in this year's draft to San Jose.
William Eklund has played four seasons in San Jose, and last season he had 53 points (15 goals and 38 assists) in 78 games.
Ottawa traded star and team captain Brady Tkachuk to Florida recently.
In Ottawa, Eklund will have two Swedish teammates, goaltender Linus Ullmark and forward Fabian Zetterlund.
Correction: An earlier version of the text contained incorrect information about which draft pick San Jose would receive in return.
