Laško was attested in written sources in 1145 under the German name Tyver (and as Tyvre in 1182, Tyuer in 1342, and Tyffer in 1461).

The Slovene name is derived from *Laško selo 'Vlach village'; the first element comes from Slavic *Vȍlxъ, referring to the Romanized Celtic population or to other Romance speakers.

[6] The German name Tüffer is believed to derive from Slavic deber 'river strait', referring to the narrowing of the Savinja River.

Stone axes discovered on the southeast slope below the old castle date back to the eighth century BC.

[8] One of the oldest buildings in Laško is called Štok or Weixelberger Manor (Slovene: Weixelberški dvor).

The property dates back to the mid-15th century, with records showing that it was given to Nikolaj Behaim by the Counts of Celje in 1437.

High water on the Savinja River also destroyed the town's bridge several times in the mid-19th century.

[12] The parish church in the settlement is dedicated to Saint Martin and belongs to the Roman Catholic Diocese of Celje.

An engineer named Rödel began to work systematically on the springs during the construction of the railway line.

The spa's reputation returned under a later owner named Gunkel, who radically renovated it and in 1882 built his own hydroelectric power plant, the first on Slovene soil, which lit up most of the buildings and the whole park.

Later the spa passed into the hands of the Pensions Institute (Pokojninski zavod) and the Central Office for Workers' Insurance (Osrednji urad za zavarovanje delavcev).

Further development mainly followed the needs of the healthcare service and to a large degree it was the fruit of cooperation with the orthopedic (later neurological, traumatology, and neurosurgical) clinics in Ljubljana, regional hospitals, and health centres across Slovenia.

[citation needed] The Laško Thermal Spa Resort is becoming one of the most important health spas and tourist centres in Slovenia.