Solum is a former municipality in Telemark county, Norway.
The parish of Solum was established as a municipality January 1, 1838 (see formannskapsdistrikt). According to the 1835 census the municipality had a population of 3,557. Solum is located west of the city Skien, and encompassed districts such as Nenset, Tollnes, Flakvarp, Skotfoss og Klyve. On 1 July 1916 an area with 1,042 inhabitants was moved to Skien, and on 1 July 1920 an area with 1,614 inhabitants was moved to Porsgrunn.
On 1 January 1964 the rest of Solum was incorporated into Skien, along with Gjerpen and Valebø district. Prior to the merger Solum had a population of 13,706.
The municipality (originally the parish) was named after the farm Solum (Old Norse Sólheimar), since the first church was built there. The first element is sól f 'Sun' (here in the sense 'sunny'), the last element is the plural form of heimr.