Hang Son Doong ('cave of the mountain river' or 'mountain cave of Doong ), also known as Son Doong cave (often without the tone marks) is a solutional cave in Phong Nha-Ke Bang National Park, Bo Trach District, Quang Binh Province, Vietnam. As of 2009 it has the largest known cave passage cross-section in the world. Less people have seen the inside of Hang Son Doong than have stood on the summit of Mount Everest.

According to World Record Application from Vietnam Book of Records, WorldKings conferred three World Record Certificates for World's Largest Natural Cave Son Doong on July 24, 2016 with three main contents below.

- Son Doong Cave is in  Phong Nha-Ke Bang National Park, Bo Trach District, Quang Binh Province, Vietnam.  Son Doong Cave‘s dimention is 200m (655ft) high, 150m(490ft) wide and at least 6.5km(4 miles) long. 

- Ho Khanh is the first person who discovered Son Doong Cave in 1991.

-  A group of scientists from the British Cave Research Association was the first to explore Son Doong Cave - World's Largest Natural Cave in 2009.

Less people have seen the inside of Son Doong Cave than have stood on the summit of Mount Everest. Therefore,after collecting documents and informaion from many different sources we officially  awarded world record certificate for "Son Doong - World's Largest Natural Cave" to Vietnam.