According to the OC Register, Scott Niedermayer will announce his retirement at a press conference at Honda Center at 1pm today.
After spending his entire career with the New Jersey Devils, who drafted him 3rd overall in 1991, Niedermayer signed with the Ducks in 2005. He has served as team captain for four of his five seasons with the team, winning a Stanley Cup in 2007 along with the Conn Smythe Trophy. Niedermayer has succeeded at literally every major championship level of the sport of hockey: Stanley Cup, Memorial Cup, World Juniors, IIHF World Championship, Olympic and World Cup.
UPDATE: A transcript of the press conference is available here.