Aldein (German: [alˈdaɪn]; Italian: Aldino [alˈdiːno]) is a comune (municipality) and a village in South Tyrol in northern Italy, located about 15 kilometres (9 mi) south of the city of Bolzano.

Aldein borders the following municipalities: Bronzolo, Montan, Deutschnofen, Auer, Truden and Ville di Fiemme. It contains the frazione (subdivision) Radein (Redagno).

A settlement called Aldinum is mentioned for the first time in 1177, in 1185 the name appears as Alden.

The coat of arms is divided party per fess; on the top are two quarter-circle, azure on argent background that represents the Weisshorn. The lower part shows the argent cross of Saint Andrew shortened that represent the four original hamlets on a gules background as the mountain of porphyrite. The arms were adopted in 1969.

According to the 2024 census, 97.89% of the population speak German, 1.85% Italian and 0.26% Ladin as first language.