| Official Name: | Wiang Kao |
| Native Name: | เวียงเก่า |
| Native Name Lang: | th |
| Settlement Type: | District |
| Subdivision Type: | Country |
| Subdivision Name: | Thailand |
| Subdivision Type1: | Province |
| Subdivision Name1: | Khon Kaen |
| Subdivision Type2: | Seat |
| Subdivision Name2: | Nai Mueang |
| Subdivision Type3: | Tambon |
| Subdivision Type4: | Muban |
| Established Title: | District established |
| Population Total: | 19750 |
| Population As Of: | 2005 |
| Blank Name Sec1: | Postal code |
| Blank Info Sec1: | 40140 |
| Blank Name Sec2: | Geocode |
| Blank Info Sec2: | 4029 |
| Timezone: | ICT |
| Utc Offset: | +7 |
| Coordinates: | 16.6786°N 102.2944°W |
Wiang Kao (Thai: เวียงเก่า, in Thai pronounced as /wīaŋ kàw/; เวียงเก่า, in Lao pronounced as /wi᷇aŋ káw/) is a district (amphoe) of Khon Kaen province, northeastern Thailand.
The major district (king amphoe) was created by splitting three tambons from Phu Wiang district. Its creation became effective on 1 May 2006.[1]
On 15 May 2007, all 81 minor districts were upgraded to full districts.[2] With publication in the Royal Gazette on 24 August the upgrade became official.[3]
Neighboring districts are (from the north clockwise) Nong Na Kham, Phu Wiang, Chum Phae, and Si Chomphu.
The district is in the Phu Wiang Mountains, parts of it in Phu Wiang National Park. In 1976 dinosaur fossils were discovered in the district. Since 2001 the discovery sites are accessible in the Phu Wiang Dinosaur Museum.
The district is divided into three sub-districts (tambons), which are further subdivided into 36 villages (mubans). There are no municipal (thesaban) areas, and a further three ambon administrative organizations (TAO).
| No. | Name | Thai name | Villages | Pop. | ||
|---|---|---|---|---|---|---|
| 1. | Nai Mueang | ในเมือง | 15 | 8,957 | ||
| 2. | Mueang Kao Phatthana | เมืองเก่าพัฒนา | 10 | 5,857 | ||
| 3. | Khao Noi | เขาน้อย | 11 | 4,936 |