O'Riordan, who played 34 AFL games for the Swans between 2016 and 2022, has been appointed to lead Sydney's AFLW program.
The 30-year-old replaces foundation coach Scott Gowans, who was axed after the Swans missed finals this year.
Since retiring from the AFL due to chronic hip injuries, O'Riordan has coached the Swans' academy team and been an assistant coach for the AFLW team.
"Ever since I arrived at the Sydney Swans as a player I fell in love with the place, so to be trusted with the role as AFLW senior coach is a huge honour," O'Riordan said.
"I have a lot of faith in the current playing list and I think we have the foundations of a successful team.
"I'm extremely grateful that the club has given me the chance to take on a more senior coaching role and I can't wait to get started."
Sydney reached the semi-finals in just their second season in the competition, but have fallen short over the past two years as superstar Chloe Molloy has suffered long-term injuries.
Swans AFLW boss Kate Mahony believes O'Riordan was the "standout choice".
"Over the past couple of years, he has shown exemplary leadership in his various coaching roles at the club, with his integrity a hallmark of his character," she said.
"Colin is a well-respected member of the club, and I look forward to seeing what he will bring to the program."
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