Harghita county is situated on the plateau of Transylvania, in the central part of the Eastern Carpathians. From the point of view of the area, Harghita County is thought of as a medium sized county and with an area of 6,639 square km, it is Romania's thirteenth county, representing 2.8% from the territory of Romania. The main characteristic of the relief is the dominancy of the mountainous area, which represents over 60% of the county's territory. In Harghita County there exists the only lake of volcanic origin in the country, the Saint Ann lake, and the biggest natural obstruction lake in the country, the ‘Red Lake' (Lacul Rosu). 

The existence of over 2000 mineral water springs is an important characteristic of the county, these are utilized for therapeutic purposes. 

The woodlands which lay on more than 30% of the county's surface, include especially fir trees, that is why we can call Harghita county an 'evergreen land'. In Harghita county's territory there are 36 protected areas, national parks and the most significant is ‘Bicaz Gorge' (Cheile Bicazului-Hasmas National Park). 

In the county there are 9 cities (Miercurea Ciuc, Odorheiu Secuiesc, Gheorgheni, Toplita, Cristuru Secuiesc, Baile Tusnad, Balan, Borsec, Vlahita) and 58 communes. 

Harghita county could be ranged in three regions: Odorhei, Ciuc and Gheorgheni, which are very well bounded both geographically and culturally and this creates a multicoloured appearance of the county.

The roads cross the county from East to West and North to East, their length is 1231 km. The 213 km long railway follows the road in the valleys of the Mures and Olt rivers.