The Queen has officially named the new cruise ship Britannia.
The 3,600-passenger vessel is the largest cruise ship designed for the British holiday market, operator P&O has said.
Its home port will be Southampton for the summer months, after being built in Italy at a cost of almost £0.5bn.
The ceremony, which Prince Philip also attended, started at about midday and marked the fifth official naming of a cruise ship by Her Majesty.
Captain Paul Brown, who gave the Queen a tour of the ship, said: "It is my great honour after 33 years at sea to show the Queen around.
"I will be showing her the atrium and the bridge then heading down to the restaurant for lunch."
Britannia bears the same name as the Queen's former Royal Yacht Britannia, which was decommissioned in 1997 after more than 40 years of service.
The 141,000-tonne ship features a 94m (308ft) union jack on its bow and will make its maiden voyage to Spain, Italy and France on 14 March.
At 330m (1,082ft), the ship is longer than the Shard is tall.
British Brut NV from the Wiston Estate Winery at Pulborough in West Sussex is being used for the naming ceremony in Britannia's home port of Southampton.
Analysis: Paul Clifton, BBC South Today transport correspondent
In style this is all about looking and feeling British, even though the parent company is American and the ship itself has been built in Italy.
There are 15 passenger decks, 13 places to eat and 13 bars, four swimming pools and nine places to enjoy the entertainment.
The days of cruising as a holiday exclusively for the rich are long gone.
One in nine British people cruise - and that makes it more popular than skiing.
The ship is being hailed as a boost to Southampton's cruise industry, which the city council said had doubled in the past 10 years.
In 2004 there were 203 cruise ship visits, bringing 532,501 passengers. In 2014 Southampton received more than 430 cruise ships, with passenger numbers exceeding 1.5 million.
Stewart Dunn, chief executive of Hampshire Chamber of Commerce, said: "It is great that Britannia will be based in Southampton.
"There was a survey a few years ago which showed that every turnaround of a cruise ship in the city is worth £2m to the local economy.
"It is also good for 'brand Southampton' indirectly as it is great publicity for the city with the Queen coming here and having the word Southampton on the side, it is promoting us wherever it goes."
The Queen has previously christened the Royal Yacht Britannia and four cruise ships Queen Elizabeth 2, Oriana, Queen Mary 2 and the Queen Elizabeth.
The Britannia cruise ship will sail from Southampton during the summer and from the Caribbean in the winter.
David Dingle, CEO of Carnival UK, the company which owns P&O said at the ceremony: "The naming of a new ship is a proud moment for any shipping line but today holds a special significance for P&O and our shared past and future.
"We are honoured the Queen is naming Britannia."