Augustinas Voldemaras (16 April 1883 – 16 May 1942) was a Lithuanian nationalist political figure. He briefly served as the country's first prime minister in 1918 and continued serving as the minister of foreign affairs until 1920, representing the fledgling Lithuanian state at the Versailles Peace Conference and the League of Nations. After some time in academia, Voldemaras returned to politics in 1926, when he was elected to the Third Seimas.

Dissatisfied with the left-wing government of President Kazys Grinius, Voldemaras and fellow nationalist Antanas Smetona supported the military coup d'état in December 1926 and he was appointed as the prime minister for a second time. A brilliant orator, Voldemaras represented the radical wing of the Lithuanian Nationalist Union that was increasingly critical of the more moderate policies of President Smetona. Smetona had Voldemaras removed from office in September 1929 and exiled to Zarasai. Voldemaras was arrested in 1934 after the failed coup against Smetona and served a prison sentence until he was exiled to France in 1938. Returning to Lithuania soon after the Soviet occupation of Lithuania, he was promptly arrested by the Soviet authorities and died in their custody in Moscow.

Voldemaras was born on 16 April 1883 in Dysna village in what is now Ignalina district municipality, Lithuania (then part of the Vilna Governorate of the Russian Empire). Though born to a family of modest means and education, Augustinas excelled at his studies. He finished public school in nearby Tverečius and graduated from a three-year school in Švenčionys. In 1890, he moved to Saint Petersburg to join his brother who had been working there. In 1902, Voldemaras passed the exams to enter a gymnasium, eventually graduating with distinction in 1904. While preparing for the exams in 1901, Voldemaras met Antanas Smetona, who would become his close friend, political collaborator, and, eventually, his political nemesis.

In 1909, Voldemaras graduated with a degree in History and Philosophy at the Saint Petersburg Imperial University and, in 1910, received his Master's Degree and was awarded a gold medal for his dissertation. A scholarship fund was set up to enable him to further his studies, and eventually, he achieved his PhD. After a period of studying in Italy and Sweden, Voldemaras returned to the university (now named Petrograd Imperial University) in 1915 and joined its staff. He moved to Perm to become a professor when the Imperial University opened its branch there (the branch would later become Perm State University). However, Voldemaras was not satisfied with the living conditions in Perm and planned his return to Lithuania.

Voldemaras first entered politics as a student in Saint Petersburg. The nationalism sweeping Lithuania in the Russian Empire included prominent voices calling for Lithuanian independence or autonomy within the Empire. Voldemaras joined the newly established Party of National Progress in 1916 and a group of Lithuanian students in Saint Petersburg, representing it at the Petrograd Seimas in June 1917 and the Congress of Non-Sovereign Nations in Kiev in September 1917. In 1918, he represented Lithuanian interests at the peace negotiations for the Treaty of Brest-Litovsk between Germany and the Soviet Russia. Since Lithuania was not part of the negotiations, he was officially part of the delegation of the short-lived Ukrainian People's Republic. His influence at the conference was minimal and Lithuania was claimed by Germany as part of the settlement.

In 1918, Voldemaras returned to Lithuania and joined the Council of Lithuania after several members left it in protest of its alignment with Germany. One of the many problems facing the council was the lack of unity among Lithuanian organizations — several were claiming to represent Lithuania on the international stage. In September 1918, Voldemaras and Smetona participated in a conference in Lausanne, Switzerland, helping to unite the organizations behind the Council of Lithuania. Events moved rapidly after the defeat of Germany in the World War I. Germany recognized Lithuanian independence and its army withdrew. The Presidium of the Council of Lithuania, which had been acting as a collective head of state, chose Voldemaras as the first Prime Minister of Lithuania and allowed him to form the government.

Voldemaras assumed power on 11 November 1918 and formed a cabinet, taking two cabinet positions for himself: the Ministry of Foreign Affairs and the Ministry of Defense. Voldemaras's first stated priority was to ensure the internal stability of the country; he hoped that a statement of neutrality would deter foreign interference for a time. Nevertheless, on 23 November, he signed the order creating the Lithuanian armed forces and appointed General Kyprian Kandratovich as Deputy Minister of Defense. This appointment proved very unpopular. Kondratovich was an ethnic Belarusian viewed with suspicion by many. He failed to take measures to organize the defense of the country and proposed to move the government to Grodno when Vilnius was threatened by a Soviet advance. He was dismissed on 24 December 1918.

Voldemaras and Smetona left Lithuania on 21 December 1918. The stated purpose of their trip was to secure a badly needed loan from Germany and to participate in the Versailles Peace Conference, but the departure generated outrage in Lithuania, where Voldemaras was seen as fleeing the Soviet advance. In absentia, he was replaced as the prime minister on 26 December 1918 by Mykolas Sleževičius. Furious with these events, Voldemaras nevertheless continued to serve as Minister of Foreign affairs and stayed in Versailles representing Lithuania.