The Roman Catholic Diocese of Alessano (Latin: Dioecesis Alexanensis) was a Roman Catholic diocese in Italy, located in the city of Alessano, in the province of Lecce, part of Apulia region of south-east Italy. On 28 June 1818, it was suppressed to the Diocese of Ugento.
Although an episcopal see of Alessano (Latin: Alexanum) may date from around 700 AD or was probably established under Norman rule around 900 AD, but the regular succession of its bishops began only in 1283 with a Giovanni from Naples. Until the 16th century, papal bulls regarding the bishopric called it either Alexanum or Leuca. It was a suffragan of the Metropolitan of Otranto.
On 17 May 1518, it was suppressed, its territory being merged into the diocese of Lecce under Bishop Giovanni Antonio Acquaviva d'Aragona, but it was restored on 3 June 1521.
Byzantine liturgical usages continued to be observed until abolished by Bishop Ercole Lamia (1578–1591).
The existence of the residential see was ended by the papal bull De utiliori of 27 June 1818 of Pope Pius VII, which assigned its territory to the then diocese of Ugento.
700: Established as Diocese of Alessano
17 May 1518: Suppressed and merged into the Diocese of Lecce