Petras Avižonis (17 April 1875 – 17 October 1939) was a Lithuanian ophthalmologist, rector of the University of Lithuania (1925–1926) and a political figure.

As a student, he was active participant in the Lithuanian National Revival, collaborating with Povilas Višinskis, Gabrielė Petkevičaitė-Bitė, Julija Žymantienė (Žemaitė).

In summer 1900, he worked with linguist Jonas Jablonskis to write a more substantial grammar, which became highly influential in creating the standard Lithuanian language.

Avižonis contributed to numerous Lithuanian periodicals, published separate brochures on medical and societal topics, and authored over one hundred academic articles.

Due to strict Russification policies, as a Lithuanian and non-Eastern Orthodox, Avižonis could only work in Lithuania if he became a priest, a doctor, or an attorney.

In June 1898, Avižonis, Višinkis, Gabrielė Petkevičaitė-Bitė, Jadvyga Juškytė and her sister Marija visited Vincas Kudirka, the publisher of Varpas living in Naumiestis in Suvalkija.

[4] They also visited Tadeusz Dowgird, archaeologist and artist, Petras Kriaučiūnas, teacher and book smuggler,[5] and Kazimieras Jaunius, priest and linguist.

[6] In August 1899, Avižonis helped organizing the first Lithuanian-language theater performance, comedy America in the Bathhouse (Amerika pirtyje), in Palanga.

After the performance, Liudas Vaineikis took Višinskis and Avižonis to Tilsit in East Prussia, the major publishing center of the illegal Lithuanian press.

[8] He continued to correspond with linguist Jonas Jablonskis, former teacher at Mitau, and with his encouragement wrote a small Lithuanian grammar based on the German-language writings of Friedrich Kurschat and on works by Kazimieras Jaunius.

[1] In 1901, he married Sofija Gruzdytė, who studied midwifery and massage in Dorpat, contributed to Lithuanian press, and published a translation of Tolstoy's The Restoration of Hell in 1908.

[1] In 1904, Avižonis assisted Jonas Jablonskis in preparing for publication the second volume of the Polish–Lithuanian dictionary, compiled by Antanas Juška.

[15] His thesis concluded that blindness in some 60% of cases resulted from trachoma and dedicated his efforts in eradicating the infectious disease.

[1] Using more than 50 pen names, he contributed numerous articles, often on medical topics, to Lithuanian press, including democratic Vilniaus žinios (1905–1909), Lietuvos ūkininkas (1905–1909), Lietuvos žinios, and social democratic Darbininkų balsas (1902), Naujoji Gadynė (1906), Skardas (1907), and others.

[1] At the outbreak of World War I, Avižonis was again drafted to serve as doctor in the Imperial Russian Army.

From December 1914 to June 1916, he worked as a senior doctor in a Red Cross sanitary train and a medical platoon.

As a member of the Lithuanian Communist Party,[17] he was invited by Vincas Mickevičius-Kapsukas to become Commissar of Health in the short-lived Lithuanian–Byelorussian Soviet Socialist Republic in 1919.

[22] He was interested in linguistics and assisted Kazimieras Būga and Juozas Balčikonis in their efforts of compiling the Academic Dictionary of Lithuanian.