The right-winger will have sports hernia surgery on Thursday in Montreal to deal with an injury that has bothered him for much of the last four months.
"Bobby has been dealing with the discomfort of this injury since it was sustained in November," Senators general manager Bryan Murray said in a statement released by the NHL team. "Both Bobby and our medical staff were hopeful that we could hold off from having surgery until the completion of the season, but he aggravated the condition last Saturday in Dallas to the point that surgery is now the only option."
Ryan, 27, missed his first two games of the season earlier this week after only sitting out a combined three games in the previous four campaigns.
The former Anaheim Duck had an outstanding start to his first season in Ottawa with nine goals and 19 points in his first 17 games through Nov. 9.
But Ryan began to struggle offensively thereafter, posting just a goal in his next five outings and mustering only 29 points in 53 games since Nov. 9.
"Bobby has worked hard to play through this injury to help his team and his teammates, and had yet to miss a game this season prior to the injury progressing to this point," Murray said of Ryan, whose 23 goals this season leads the club.
Ryan topped 17 minutes of ice time in eight of his first 17 games but only 18 times since in 53 starts, an indication that his body couldn't handle the same workload.
"We're confident that he'll recover in time to have a full summer of training that will allow him to be back in our lineup and help this team be successful next season."
The Senators entered play Thursday out of the playoff picture in the Eastern Conference, sitting 12th with a 29-29-14 record, eight points behind the eighth-place Detroit Red Wings.
Ottawa hosts the Florida Panthers on Friday at 7:30 p.m. ET.