Her Majesty The Queen has officially named a huge new cruise ship, Britannia.
It weighs 141,000 tonnes, can hold more than 3,500 passengers and is over 300 metres long.
It's the fifth time the Queen has had the honour of naming a cruise ship.
She's previously christened the Royal Yacht Britannia and four cruise ships: Queen Elizabeth II, Oriana, Queen Mary II and the Queen Elizabeth.
But have you ever thought about how a ship gets its name?
Many big boats are named by the firms that make them, others can be named by the Queen or other VIPs. Martin's got more.