The slate landscape of north-west Wales became the 32nd site in the UK to join the esteemed list, granted by the World Heritage committee.
Running through Gwynedd, it became the world leader for the production and export of slate in the 1800s.
Heritage minister Caroline Dinenage said: “Unesco World Heritage Status is a huge achievement and testament to the importance this region played in the industrial revolution and Wales’ slate mining heritage.
“I welcome the prospect of increased investment, jobs and a better understanding of this stunning part of the UK.”
The committee was scouting out a unique landmark with a cultural, historical or physical significance.
It is the second site in the UK to be awarded Unesco Heritage status in 2021.
The City of Bath was also added to the Unesco World Heritage List as part of the great spa towns of Europe.
It makes the City of Bath only the second place in the UK with a double Unesco listing after it was originally inscribed on the Word Heritage List in 1987.
Other areas awarded the prestigious title this year include the Trans-Iranian Railway and an underground Roman gold mining complex in Romania.
The Welsh Slate Industry
By the 1890s, the Welsh slate industry employed around 17,000 workers and produced almost 500,000 tonnes of slate a year, around a third of all roofing slate used in the world in the late 19th century.
The industry had a huge impact on global architecture with Welsh slate used on a number of buildings, terraces and palaces across the globe including: Westminster Hall in London’s Houses of Parliament, the Royal Exhibition Building, Melbourne, Australia and Copenhagen City Hall in Denmark.
First Minister of Wales Mark Drakeford said its recognition by Unesco will help preserve its history and legacy for generations to come.
He said: “Today’s announcement recognises the significant contribution this part of North Wales has made to the cultural and industrial heritage not only of Wales, but of the wider world,” he said.
“Welsh slate can be found all over the world.
“The quarrying and mining of slate has left a unique legacy in Gwynedd, which the communities are rightly proud of.”