Thürnen is a municipality in the district of Sissach in the canton of Basel-Country in Switzerland.
Thürnen has an area, , of . Of this area, or 56.9% is used for agricultural purposes, while or 25.3% is forested. Of the rest of the land, or 18.7% is settled (buildings or roads).
Of the built up area, housing and buildings made up 11.1% and transportation infrastructure made up 5.3%. Out of the forested land, 22.7% of the total land area is heavily forested and 2.7% is covered with orchards or small clusters of trees. Of the agricultural land, 16.4% is used for growing crops and 28.0% is pastures, while 12.4% is used for orchards or vine crops.
The blazon of the municipal coat of arms is Or, a two-arched towered Bridge Sable and Coupeaux Vert. The design was created in 1944. The castle in the coat of arms came from an oral tradition that held that the name Thürnen meant "at the towers". The colors come from the Homburg region, which once contained the municipality.
Thürnen has a population () of . , 18.2% of the population are resident foreign nationals. Over the last 10 years (1997–2007) the population has changed at a rate of 18.7%.
Most of the population () speaks German (1,041 or 89.2%), with Italian language being second most common (56 or 4.8%) and Serbo-Croatian being third (26 or 2.2%). There are 15 people who speak French.
the gender distribution of the population was 50.8% male and 49.2% female. The population was made up of 1,086 Swiss citizens (79.7% of the population), and 277 non-Swiss residents (20.3%) Of the population in the municipality 264 or about 22.6% were born in Thürnen and lived there in 2000. There were 413 or 35.4% who were born in the same canton, while 303 or 26.0% were born somewhere else in Switzerland, and 172 or 14.7% were born outside of Switzerland.
In there were 7 live births to Swiss citizens and 1 birth to non-Swiss citizens, and in same time span there were 4 deaths of Swiss citizens. Ignoring immigration and emigration, the population of Swiss citizens increased by 3 while the foreign population increased by 1.