Which ocean liner was the first to feature a planetarium at sea?

RMS Queen Mary 2 was the first ocean liner to feature a planetarium at sea.

The Cunard liner’s planetarium, known as Illuminations, opened as part of the ship’s onboard entertainment and educational facilities. It uses a dome theater to present astronomy programs and other visual shows during voyages.

Queen Mary 2 entered service in 2004 as a purpose-built ocean liner for transatlantic crossings. Unlike most modern cruise ships, which are primarily designed for leisurely itineraries, she was engineered for regular service between Southampton and New York and has a hull suited to the open Atlantic.

The planetarium is sometimes confused with a standard cinema or theater. Illuminations has also served as a lecture and performance venue, but its distinctive feature is the dome-based astronomy experience. Queen Mary 2 also carries a maritime tradition associated with earlier Cunard flagships.