The event at Meyer Werft shipyard in Germany marked the start of construction of the 999-passenger ship, which is due to start service from Dover in August 2020.
Saga is due to welcome its first new-build ship, Spirit of Discovery, to its fleet in July 2019.
Nigel Blanks, chief operating officer for Saga Cruises, said: “Today marks a special moment in Saga Cruises’ history – the first steel cutting of Saga’s second purpose built cruise ship, Spirit of Adventure.
“Built by the same expert team at the Meyer Werft shipyard, she is a beautiful sister ship to Spirit of Discovery.
“With her striking design, distinctive new venues and innovative speciality restaurants, Spirit of Adventure will certainly have a unique personality and will fulfil our promise of boutique luxury, perfectly.”
Spirit of Adventure will operate itineraries to the Norwegian fjords, Caribbean and Mediterranean when it launches next year.