RANKED: The 17 biggest private luxury yachts in the world

The biggest private luxury yachts in the world have been revealed by Boat International, a yachting lifestyle website.

Of the top 17, lengths range from 123 metres/404 feet all the way up to a massive 180 metres/591 feet.

While most were constructed this century, the oldest on the list was first launched 150 years ago.

Many of the top 17 luxury yachts have hidden histories, and despite their size it's unknown who owns them.

Here are the world's biggest luxury yachts: