Băile Tuşnad is a city in Harghita County, Transylvania , Romania. With a population of 1,728, it is the smallest city in "Romania" by population. It is located at an altitude of 650 metres in the southern reaches of the Ciuc depression, between the Harghita and Bodoc mountains, in the valley of the Olt, and is to this day an important spa town. The village of Carpitus/Kárpitus is administratively part of the city.

The most probable date for the founding of the bathing station is 1842. The miraculous healing of the son of a shepherd first attracted widespread attention to the therapeutic properties of Băile Tuşnad's mineral waters, after which a company was founded to exploit the springs in 1845. The station was destroyed in the 1849 revolution, but reconstruction began in 1852.

The town and the surrounding area are famous for their spas and mineral waters. Nearby is the famous volcanic crater lake, the only one of its kind in Romania, called Lake Sfânta Ana (Saint Anne Lake). It is an important site of cultural importance for the Székely people.