Baldus de Ubaldis (Italian: Baldo degli Ubaldi; 1327 – 28 April 1400) was an Italian jurist, and a leading figure in Medieval Roman Law and the school of Postglossators.
A member of the noble family of the Ubaldi (Baldeschi), Baldus was born at Perugia in 1327, and studied civil law there under Bartolus de Saxoferrato, being admitted to the degree of doctor of civil law at the early age of seventeen. Federicus Petrucius of Siena is said to have been the master under whom he studied canon law.
On his promotion to the doctorate he went to Bologna, where he taught law for three years, after which he was advanced to a professorship at Perugia, where he remained for thirty-three years, and he had among his students Francesco Albergotti. He subsequently taught law at Pisa, Florence, Padua and Pavia, the rivals to Bologna. During his period at Pavia he sometimes also taught at Piacenza. He died at Pavia on 28 April 1400 and was buried in the church of San Francesco.