Petras Leonas (1864–1938) was a Lithuanian attorney and politician, the first Minister of Justice of the newly independent Lithuania in 1918.
After graduating from Moscow University in 1889, Leonas held a government job at various courts in Suwalki and Uzbekistan.
He was fired after supporting the Constitutional Democratic Party (Kadets) during the Russian Revolution of 1905.
He returned to Lithuania and took up private law practice, which he had for 32 years.
In 1907, he was elected to the second short-lived State Duma of the Russian Empire.
During World War I, Leonas retreated to Russia and was deputy chairman of the Lithuanian Society for the Relief of War Sufferers.
In March 1917, he was one of the founders of the Democratic National Freedom League.
He returned to newly independent Lithuania in 1918 and began working on drafting some of the fundamental legislation.
He became the first Minister of Justice in November 1918 and the fourth Minister of Internal Affairs in April 1919.
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 became a professor and dean of the Law Faculty at the University of Lithuania.