Hạ Long Bay or Halong Bay is a UNESCO World Heritage Site and popular travel destination in Quảng Ninh province, Vietnam. The name Hạ Long means "descending dragon". Administratively, the bay belongs to Hạ Long city, Cẩm Phả city, and is a part of Vân Đồn district. The bay features thousands of limestone karsts and islets in various shapes and sizes. Hạ Long Bay is a center of a larger zone that includes Bai Tu Long Bay to the northeast, and Cát Bà Island to the southwest. These larger zones share a similar geological, geographical, geomorphological, climate, and cultural characters.

Quảng Ninh or Quangninh is a province along the northeastern coast of Vietnam. It is about 153 km (95 mi) east of Hanoi, comprising four cities, two district-level towns and seven rural districts. The provincial capital is Hạ Long. The province covers an area of 6,207.95 km2 (2,396.90 sq mi) and, as of 2023, had a population of 1,413,452. Nearly 80% of the province is mountainous with abundant land, forest, water and mineral resources, with 90% of Vietnam's coal output extracted from the province. The province is also home to Hạ Long Bay, a World Heritage Site that has 1,969 islands, out of which 989 have been given names.