Petras Leonas (1864–1938) was a Lithuanian attorney and politician, the first Minister of Justice of the newly independent Lithuania in 1918.

He worked to organize judicial system and establish local municipal institutions in the chaotic post-war years.

He retired from active politics in October 1919, but continued to consult the Lithuanian government on major pieces of legislation.

Leonas, the youngest of 11 children, was born on 16 November 1864 in Leskava [lt] near Gudeliai, Suwałki Governorate, to a family of Lithuanian farmers.

[2] With financial help from his eldest brother priest Silvestras Leonavičius,[3] Leonas continued his studies at the law faculty of Moscow University.

He worked as a court interrogator in Tashkent, as justice of the peace and assistant prosecutor in Samarkand, and district judge in Margilan.

[2] He returned to Lithuania in September 1906 taking up private attorney practice in Kaunas and joining Lithuanian cultural life.

[7] In 1907, Leonas was elected to the second State Duma of the Russian Empire where he joined the Constitutional Democratic Party (Kadets).

[9] The outbreak of World War I presented an opportunity for Lithuanians to seek autonomy if not independence from the Russian Empire.

[8] However, the Committee soon disbanded as its chairman Leonas resigned in January 1915 in protest of Andrius Bulota's and Mykolas Januškevičius' withdrawals from the Lithuanian Society for the Relief of War Sufferers.

[10] In mid 1915, during the Great Retreat of the Russian Imperial Army, Leonas evacuated from Lithuania to Russia where he continued to work on the war relief efforts becoming vice-chairman of the Lithuanian Society.

[8] In March 1917, Leonas was one of the founders of the Democratic National Freedom League, a party of secular and liberal platform that is often known simply as Santara.

[12] As a minister, Leonas propagated the ideas of Rechtsstaat (rule of law) and worked to organize, standardize, and improve the judicial system and local municipal institutions.

[14] Already in early 1918, together with Tadas Petkevičius and Kostas Jablonskis, he began working on laws governing administrative divisions and local self-government.

[12] Leonas also worked on drafting other fundamental laws, including on elections, passports, societies and associations, press, but most of those became effective after his tenure.

[12] Together with Antanas Tumėnas, he represented priest Konstantinas Olšauskas accused of murder during his high profile trial in October 1929.

As a respected authority on legal matters, Leonas was considered several times by the Seimas for President of Lithuania.

[12] The university found a loophole – Leonas was elected as an honorary professor and could continue to lecture albeit with no compensation.

Instead of buying flowers for his funeral, mourners were asked to donate the money to struggling students and victims of a large fire in Palanga.