| Official Name: | Wiang Kaen |
| Native Name: | เวียงแก่น |
| Native Name Lang: | th |
| Settlement Type: | District |
| Subdivision Type: | Country |
| Subdivision Name: | Thailand |
| Subdivision Type1: | Province |
| Subdivision Name1: | Chiang Rai |
| Subdivision Type2: | Seat |
| Subdivision Name2: | Muang Yai |
| Subdivision Type3: | Tambon |
| Subdivision Type4: | Muban |
| Established Title: | District established |
| Population Total: | 32310 |
| Population As Of: | 2005 |
| Blank Name Sec1: | Postal code |
| Blank Info Sec1: | 57310 |
| Blank Name Sec2: | Geocode |
| Blank Info Sec2: | 5713 |
| Timezone: | ICT |
| Utc Offset: | +7 |
| Coordinates: | 20.1122°N 100.5136°W |
Wiang Kaen (Thai: เวียงแก่น; in Thai pronounced as /wīaŋ kɛ̀n/) is the easternmost district (amphoe) of Chiang Rai province, northern Thailand.
Historically, the area was Mueang Wiang Kaen, on the Ngao River. It was founded about the same time of Sukhothai Kingdom and Chiang Rai.
The government separated the three tambons Muang Yai, Po, and Lai Ngao from Chiang Khong district to create a minor district (king amphoe) on 1 April 1987.[1] It was upgraded to a full district on 7 September 1995.[2]
Neighboring districts are (from the south clockwise) Thoeng, Khun Tan, Chiang Khong of Chiang Rai Province. To the east lies Bokeo province of Laos.
Phu Chi Fa, 1,442 m high, lies at the border with Thoeng District.[3]
The district is divided into four sub-districts (tambons), which are further subdivided into 41 villages (mubans). There are no municipal (thesabans), and four tambon administrative organizations (TAO).
| No. | Name | Thai name | Villages | Pop. | ||
|---|---|---|---|---|---|---|
| 1. | Muang Yai | ม่วงยาย | 9 | 7,449 | ||
| 2. | Po | ปอ | 20 | 15,946 | ||
| 3. | Lai Ngao | หล่ายงาว | 6 | 3,490 | ||
| 4. | Tha Kham | ท่าข้าม | 6 | 5,425 |