Born in Bocșa, Szilágy County, Transylvania. He became a teacher of history at the secondary school in Blaj, which was at the time, like the rest of Transylvania, part of the Austrian Empire. Bărnuțiu was influenced early-on by the philosophy of Immanuel Kant, in which he saw the means to reform society in opposition to traditional theological views, while supporting a presence of laity in the administrative structures of his own church. An active contributor to Foaie pentru minte, inimă și literatură, the literary supplement of George Barițiu's journal Gazeta de Transilvania, he became noted after 1842 for virulently opposing the decision of the Magyar-dominated Transylvanian Diet to give Hungarian a status of a semi-official language in local administration of Transylvania. On March 24, 1848, Bărnuțiu issued one in a series of appeals by various authors, calling for self-determination of Romanians inside Transylvania, viewing it as a necessary step in matching Magyar success in obtaining rights from Emperor Ferdinand I, and professing that Romanians should reject the projected union of the region with the Kingdom of Hungary until ensured proportional representation and the official condemnation of serfdom.
The Blaj Assembly convened in April on the basis of such proclamations gathered together intellectuals, clergy, and commoners. Bărnuțiu gave several speeches in front of the Assembly, calling for patience and moderation while continuing to campaign against all unilateral change in Transylvania's government and disagreeing with more skeptical political leaders, such as Bariț and Andrei Șaguna, and finally being persuaded to include an oath of allegiance to the Emperor in his political strategy. Just before the Second Assembly in May, he agreed to moderate his tone further, taking in view the points made by Bariț in regard to the fragile situation facing Romanians in the region, and partly reformulated his program on self-determination. On May 17, he was elected vicepresident of the Permanent Committee formed by Blaj delegates as a supervising body, later the basis of the National Romanian Committee. The rapid succession of events after the proclamation of Transylvania's union with the Hungarian Kingdom and of Hungary's independence, with an Austrian military debacle in Transylvania, saw a rapprochement between the loyalist Austrian Anton Freiherr von Puchner, nominal governor of the region, and Bărnuțiu's Committee. From the Committee's perspective, this was an Austrian recognition of Transylvania's self-government as a Romanian region, which was to be advanced to the new emperor Franz Josef.
After Imperial Russian intervention in Transylvania, he decided to go into exile, and settled in Iași, Moldavia's capital. He wrote several treaties on law and philosophy, and, before and after the union of the Danubian Principalities under DomnitorAlexandru Ioan Cuza advocated radical reforms which were a direct inspiration to the Moldavian liberal dissidents grouped as Fracțiunea liberă și independentă. In the 1850s, Bărnuțiu wrote against the popular project of electing a foreign prince as ruler of the Principalities, an opposition which Fracțiunea carried into the Constituent Assembly following the toppling of Cuza two years after Bărnuțiu's death. Junimea, a conservativeliterary society created during that period, criticized him along with other Transylvanian intellectuals for having supported a Romanian grammar and alphabet based on Latin etymologies instead of one reflecting the spoken language. After having fallen gravely ill, Simion Bărnuțiu asked to be allowed to return to his native village. He died on the way there, in Hida.
