| Official Name: | La-un |
| Native Name: | ละอุ่น |
| Native Name Lang: | th |
| Settlement Type: | District |
| Subdivision Type: | Country |
| Subdivision Name: | Thailand |
| Subdivision Type1: | Province |
| Subdivision Name1: | Ranong |
| Subdivision Type2: | Seat |
| Subdivision Name2: | La-un Tai |
| Subdivision Type3: | Tambon |
| Subdivision Type4: | Muban |
| Established Title: | District established |
| Population Total: | 12506 |
| Population As Of: | 2005 |
| Blank Name Sec1: | Postal code |
| Blank Info Sec1: | 85130 |
| Blank Name Sec2: | Geocode |
| Blank Info Sec2: | 8502 |
| Timezone: | ICT |
| Utc Offset: | +7 |
| Coordinates: | 10.115°N 98.75°W |
La-un (th|ละอุ่น, pronounced as /th/) is a district (amphoe) of Ranong province, southern Thailand.
In 1932 the minor district (king amphoe) was established as a subordinate of Mueang Ranong district. On 28 June 1973, it was upgraded to a full district.[1] In 1996, a new district office was built.
Neighboring districts are (from the north clockwise) Kra Buri of Ranong Province, Sawi, Lang Suan and Phato of Chumphon province, and Mueang Ranong of Ranong. To the west across the estuary of the Kraburi River is the Tanintharyi Division of Myanmar.
The district is divided into seven sub-districts (tambons), which are further subdivided into 35 villages (muban). La-un itself is a township (thesaban tambon) and covers parts of tambons La-un Tai and Bang Phra Tai. There are a further three tambon administrative organizations (TAO).