Lang Rongrien (Thai: หลังโรงเรียน, lit. 'behind the school') is a rock shelter and Hoabinhian habitation site in the upland region of Krabi province in west-coast southern Thailand. The site is of the Pleistocene, early Holocene archaeological time frame. Excavations at the site began in 1974, and primary research was headed by Douglas Anderson. Though this rock shelter site is not as large as some others, it is archaeologically rich in its findings. Some of the sediment at the site was disturbed by soil collections, but not enough to have ruined the more impressive archaeological finds. The site is located within the Krabi River valley, in a somewhat hard-to-reach area that can only be accessed from a steep trail below the rock shelter, or a narrow ridge that approaches the rock shelter from the north. Radiocarbon dating at the site has put the evidence from between 39,000 and 28,000 years before present.
Hoabinhian habitation sites are most often found in rock shelters and are found all across southeast Asia. The Hoabinhian hunter-gatherers who lived at the Lang Rongrien rock shelter used the site as a temporary habitation site, inhabited on a seasonal basis. There are multiple generations of inhabitants at Lang Rongrien. The oldest use for the rock shelter was as a campground for hunters in the late Pleistocene epoch. In the early Holocene epoch the rock shelter was also used for habitation. The last time the site was inhabited about 4,000 years ago it was used again as a campground, but was also used as a grave site. All of these distinct periods of habitation at the rock shelter contain periods of time in-between when no one seemingly inhabited the site at all.
The dating at Lang Rongrien was done by radiocarbon dating pieces of charcoal that come from the stratigraphic layers. The oldest pieces of charcoal found in the lowermost layers where human habitation is seen have been dated to around 39,000 years ago. A piece of charcoal found in the 7th layer has been dated to almost 45,000 years ago, but this is likely because it came from the roof fall, and does not indicate anything about human habitation at this site. Charcoal pieces from the upper layers have been dated to about 9,000 years ago. The most recent dates from the site come from pieces of pottery found with the burial goods and are placed at an age of 3,000 to 5,000 years ago.