Wiang Nong Long (, ) is a district (amphoe) of Lamphun province, northern Thailand.
The minor district (king amphoe) was split off from Pa Sang district becoming effective on 1 April 1995.
On 15 May 2007, all 81 minor districts were upgraded to full districts. With publication in the Royal Gazette on 24 August, the upgrade became official.
Neighboring districts are (from the east clockwise) Pa Sang and Ban Hong of Lamphun Province, Chom Thong and Doi Lo of Chiang Mai province.
The district Wiang Nong Long is divided into three sub-districts (tambon), which are further subdivided into 25 administrative villages (Muban).
There are three sub-district municipalities (Thesaban Tambon) in the district: