The Triestine dialect (Italian: triestino, Triestine: triestin) is a dialect local to the Italian city of Trieste. It is a form of Venetian, strongly influenced by a Friulian substrate, mainly due to the existence of the now extinct Tergestine dialect, which was closely related to Friulian.
Many words in Triestine are taken from other languages. As Trieste borders with Slovenia and was under the Habsburg Monarchy for almost six centuries, many of the words are of German and Slovene origin. Due to extensive emigration to the city in the late 18th and 19th centuries, many words also came from other languages, such as Greek and Serbo-Croatian.
After the expansion of the Republic of Venice, from the Middle Ages onwards, Venetian gradually asserted itself as a lingua franca in parts of the Eastern Mediterranean and in the Adriatic Sea, eventually replacing or strongly influencing several coastal languages such as the dialects of Trieste and Istria and also the Dalmatian dialects of Zara (Zadar) and Ragusa (Dubrovnik). In Trieste, this resulted in the gradual replacement of the former Tergestine dialect (related to Friulian within the Rhaetian subgroup of Romance languages) and of the neighbouring Slovene dialects by a Venetian-based language. This phenomenon began to take place first among fishermen and sailors, while the traditional bourgeoisie continued to speak Tergestine until the beginning of the 19th century. By that time, Tergestine was virtually a dead language, and the period of Modern Triestine had begun.