Leon Jan Piniński (8 March 1857 – 4 April 1938) was a Polish scholar, diplomat, art historian and politician.

In 1891 he became a professor of Roman law at his alma mater and was elected to membership of the Polish Academy of Arts and Sciences.

Extremely conservative, in 1903 he was dismissed from office and replaced by the politically liberal industrial mogul, Andrzej Kazimierz Potocki.

Although Piniński retained his seat in the Austro-Hungarian Senate, he retired from public life and devoted himself to advanced studies of law as well as art history.

A large part of his collection, which included English prints, was later stolen by the Germans during World War II and was never returned to Poland.