Dârjiu is a commune of 850 people (2021) in Harghita County. It lies in the Székely Land, an ethno-cultural region in eastern Transylvania. Over 90% of the residents were ethnically Hungarian in 2021.

The commune is composed of two villages, Dârjiu (Székelyderzs) and Mujna (Székelymuzsna), both of which are on the route of the Via Transilvanica long-distance trail.

They are part of the "heartland of Unitarianism" in Romania.

• 46.20220225.1992341 The fortified church (Biserica fortificată). This 14th-century fortified Unitarian Church was built by the Székely Hungarian community. Now it is a UNESCO world heritage site. The murals of the church show the legend of Ladislaus I of Hungary. When the Cumans broke into Kingdom of Hungary, Ladislaus, still a Duke, along with his cousin (King Salamon (Solomon) I) rode against them and freed from a Cuman a girl believed to be daughter of an aristocrat.  
• Further murals in the region are to be found at Unitarian churches in Mugeni, Crăciunel (Karácsonyfalva; part of Ocland commune), and smaller ones in Rugănești (Rugonfalva; part of Șimonești commune) and Cristuru Secuiesc (Székelykeresztúr). The most significant murals in Saxon churches are those of Mălâncrav (Hungarian: Szászszentlászló; part of Laslea commune).