The Editio Leonina or Leonine Edition is the edition of the works of Saint Thomas Aquinas originally sponsored by Pope Leo XIII in 1879.
The Leonine Commission (Commissio leonina) is the group of scholars working on the ongoing project of critically editing the works of Aquinas. The first superintendent of the commission was Tommaso Maria Zigliara, professor and rector of the Collegium Divi Thomae de Urbe (the future Pontifical University of Saint Thomas Aquinas). Its current seat is in Paris, rue de la Glacière and it is currently (as of 2015) chaired by friar Adriano Oliva. The editions are published with editions du Cerf, the historical Dominican publishing house in France founded in 1929 at the request of Pope Pius XI.
Aquinas' main work, the Summa Theologiae, was edited in nine volumes (tt.IV–XII) during 1888–1906. As of 2014, the Editio Leonina comprises 39 volumes, representing about half of the entire scope of the project.