The British capital has topped the poll at the annual Travellers' Choice awards, beating Paris and Bali to the crown.
Hayley Coleman, TripAdvisor spokesperson, said in a statement: "The global fascination with Harry and Meghan clearly has a powerful effect as this is the first time since 2016 that London has topped the world rankings. With the couple's new Royal baby due imminently, London may continue to reap the rewards of the Harry and Meghan effect into 2020."
Whilst Laura Citron, CEO of tourist board Visit London, added: "London has an exciting history as a centre for creativity and free thinking, from Shakespeare to the birth of punk and the catwalks of today. This creative energy and cultural vibrancy can be felt in every aspect of London life: food, fashion, arts, exhibitions, shops, and nightlife."
In the list, which has the top 25 best-rated destinations in the world according to the site, Rome, Crete and Phuket make the list as well as Barcelona, Istanbul and Marrakech, with Dubai completing the top 10.
Elsewhere, London topped the poll for the best-rated destinations in the UK and Channel Islands, with Edinburgh, Liverpool, Glasgow and Belfast rounding out the top five. Bath, Isle of Wight, York, Manchester and Jersey completes the top 10.