Telšiai (pronunciation^ⓘ; Samogitian: Telšē) is a city in Lithuania with about 21,499 inhabitants. It is the capital of Telšiai County and Samogitia region, and it is located on the shores of Lake Mastis.

Telšiai is one of the oldest cities in Lithuania, probably dating earlier than the 14th century. Between the 15th and 20th centuries, Telšiai became a district capital. Until 1795, Telšiai County formed the Duchy of Samogitia within the Grand Duchy of Lithuania. Between 1795 and 1802 it was included in the Vilnius Governorate. In 1873, Telšiai was transferred to the Kovno Governorate.

The name Telšiai is a variant of the same Lithuanian language root (-telš-, -tilž-) as Tilžė or Talsi with the meaning connected to water. The name Telšiai or Telšē in Samogitian dialect of Lithuanian is derived from a verb telkšoti (literally, to be flooded with water, to splash, etc.). It is a cognate to the Greek thalassa - sea, compare the river Jūra - a sea flowing in the same longitude territory. It may also relate to the sum of 45° longitude of Greenwich as the core of Europe or also all western side or one fourth in the West of The Eastern Hemisphere.

The name of Telšiai has been recorded in different forms and different languages throughout its history. Most of them are derived from Telšē in Samogitian dialect. Some foreign names for the city include Latvian: Telši; German: Telschen, Telschi; Polish: Telsze; Russian: Тельшяй, Тельши, Тяльшяй. In Yiddish, the name is טעלז‎ (Telz). In English sources, Telšiai are known also by several alternative names, including Telsiai, Telshi and Telschi.

Lake Mastis is mentioned in various legends and myths. The city was named after a small rivulet, the Telšė, which flows into Lake Mastis. A legend has it that a knight named Džiugas founded the city. First mentions of Telšiai date back to 1398, but the oldest archeological findings in the area of the city are from the Stone Age. In the 15th century, Telšiai already had a state-owned manor. It and the parish were governed by Samogitian elders. Telšiai was at the centre of an uprising of Samogitian peasants.

At the end of the 17th century Telšiai became the centre of culture and politics of Samogitia. Local parliaments known as Sejmiks composed of noblemen were organised in the city and a court was established. Magdeburg rights were granted to Telšiai in the 17th century. Until the Third Partition of Polish-Lithuanian Commonwealth in 1795, Telšiai County formed the Duchy of Samogitia in the Grand Duchy of Lithuania within the Polish–Lithuanian Commonwealth.

During the November uprising of 1831 Telšiai became a sanctuary for Polish–Lithuanian partisans fighting the Russians. A revolutionary government of insurrectionists was formed and schools for the preparation of military officers and noncommissioned officers were opened. During the Uprising of 1863, Telšiai was one of the main centres of uprise in Samogitia since insurrectionist forces massed there.

At the end of the 19th century Telšiai started to grow. A team of firemen formed, and a pharmacy and a theater were opened. In 1908 the very first Lithuanian concert–performance was organised. Telšiai was the birthplace and residence of famous Samogitian noble brothers: Stanisław Narutowicz (member of the Council of Lithuania) and Gabriel Narutowicz (the first President of Poland, who was assassinated).