Last year, the coveted award was presented to the Guinness Storehouse in Dublin.
Titanic Belfast is a six-floor building featuring nine interpretive and interactive galleries exploring the sights, sounds, smells and stories of Titanic, as well as celebrating the city and the people who built the doomed ocean liner.
Among the three million visitors from 145 different countries who have passed through its doors are the Queen, former US Secretary of State Hillary Clinton, film director James Cameron and celebrities such as Adele and Michael Buble.
Northern Ireland's First Minister Arlene Foster has praised the success of the venue.
"Titanic Belfast is now a global brand, which has put Northern Ireland on the map for all the right reasons, so official confirmation that it is now Europe's leading tourist attraction is well deserved."
Deputy First Minister Martin McGuinness said it was a "phenomenal achievement" to have won.
"The story of the Titanic is known around the globe and it is only right and proper we have a world-class visitor attraction to match," he said.
Titanic Belfast was also recently included in Lonely Planet's Ultimate Travelist of 500 of the world's most striking locations.
It will now go on to compete for the title of world's leading attraction at a ceremony in the Maldives later this year.
