Built in 1991, the 2,390-passenger ship will be transferred to Royal Caribbean's Madrid-based sister company, Pullmantur Cruises, on April 1, 2013.
The Monarch currently sails three- and four-night round-trip Bahamas cruises from Port Canaveral. It will embark on its last sailing for Royal Caribbean on March 29, 2013.
Royal Caribbean said a potential replacement for the ship's short Bahamas product would be announced in the coming months.
"She will go on creating wonderful travel memories through her final sailings for our brand through next March and then continue doing the same for Pullmantur's guests," said Adam Goldstein, president and CEO of Royal Caribbean International, in a statement.
The Monarch will increase Pullmantur's total guest capacity by nearly 25%, and bring the Spanish line's fleet of former Royal Caribbean Cruises family ships to five. The line currently operates the Monarch's sister-ship, the former Sovereign of the Seas, as well as the former Empress of the Seas, Celebrity Zenith and Celebrity Horizon.
With the reduction, Royal Caribbean will have 21 cruise ships. The line said that it has not booked anyone on the ship after March 2013, so there's no need to re-accommodate any passengers
Wonder which ship will replace Monarch?