The move will create a late-preseason competition between Ryan and Colton Schmidt, who has punted for the Bills since 2014.
Schmidt has punted six times this preseason and ranks 13th in net average (41.3 yards per punt). Ryan ranks last among NFL punters this preseason, averaging 29.8 net yards per punt.
The Bills lost backup punter Cory Carter to a torn ACL in last Friday's preseason game against the Cleveland Browns. Carter was waived/injured on Sunday. With Ryan in house, the Bills released kicker Tyler Davis.
Ryan announced Monday on Twitter that he has been released. NFL Network reported that the release was requested by Ryan, who had played for the Seahawks since 2008.
The move had been expected since the Seahawks traded up in the fifth round in April's draft to select Michael Dickson from Texas.
Ryan, 36, holds the Seahawks' franchise record for most punts (770), most punt yards (34,491), most punts inside the 20 (276) and longest punt (77). His 159 consecutive games played are also a franchise record.
ESPN's Brady Henderson contributed to this report.