Singer and actor York will officially christen the ship during a ceremony in Amsterdam on May 28, the line has said.
York has previously starred as part of the Crystal on Broadway programme, which aims to bring some of Broadway’s biggest and boldest shows to theatres and lounges across the Crystal fleet.
She will next perform on Crystal Mahler’s cruise from Amsterdam to Budapest, departing May 28.
Tom Wolber, Crystal president and chief executive, said: “Rachel’s tremendous talents and charm transcends demographics and connects with audiences throughout the world.
"We are so pleased she is part of the Crystal family, as her grace and passion for excellence are representative of the experience found aboard Crystal voyages.”
York’s latest project is Head Over Heels, a new musical comedy produced by Gwyneth Paltrow and Jordan Roth, featuring hits from the GO-GOs.
She has previously starred in City of Angels, Victor/Victoria with fellow Crystal godmother Dame Julie Andrews, and most recently, Disaster! The Musical.
“It has been a privilege to be part of... the Crystal on Broadway programme and I am honoured to be the godmother of Crystal Debussy,” said York.
“To fulfil such an enduring tradition and represent a ship of such style and elegance, as well as a crew dedicated to superb service and experiences day in and day out, is truly my pleasure.”
Crystal Debussy has capacity for 106 guests and made its maiden voyage along the Rhine on April 9, with halts in the Netherlands and Belgium during a seven-day itinerary while 10-day voyages also stop additionally in Germany.
During 2018 and 2019, the ship will sail seven and 10-day routes between Amsterdam and Basel along the Rhine and Moselle rivers.