Josh Kennedy has stepped down as Sydney co-captain, with Callum Mills promoted in his place to lead alongside Luke Parker and Dane Rampe.
Kennedy was sole captain in 2017 and 2018 before sharing the role for the past three years.
But the 33-year-old, who will remain part of the club's leadership group, felt it was the right time to step aside and allow Mills to flourish.
"Josh approached me midway through last season and said, 'Millsy's ready'," Swans coach John Longmire said.
"To identify that, foster it, and then make a selfless decision, sums up the sort of person Josh is. I know he will continue to be an important mentor."
Mills, a product of the Swans' Academy, was elevated to Sydney's leadership group during the 2018 pre-season as a 21-year-old.
Now 24, Mills has played 110 games for the Swans.
"We're here for a short time in the scheme of things and it's our duty to take that baton when it's our turn and then pass it on when the time comes - and for me that time is now," Kennedy said.
The three co-captains and Kennedy are joined by Tom Papley, Harry Cunningham and Lance Franklin in a seven-man leadership group.
Meanwhile, Luke Shuey will skipper West Coast for a third straight season, while Nic Naitanui has been promoted to vice-captain for the first time.
Shuey managed just 20 games over his first two years as captain after being struck down by calf and hamstring issues.
The 31-year-old suffered another scare at training last week when he injured his hamstring, but scans showed only a minor strain and he's expected to resume full duties within weeks.
Naitanui was promoted to joint vice-captain alongside Jeremy McGovern after veteran forward Josh Kennedy stepped down from the role.
Tom Barrass, Liam Duggan and Oscar Allen round out the formal leadership group.
"The players strongly endorsed Luke in the role for a third successive season," Eagles coach Adam Simpson said.
"He is a highly respected player and person within the club and it came as no surprise that his peers again supported his appointment.
"Gov has also been an integral part of the leadership team for the last few years while Nic steps up for the first time officially."
