Adalbert III of Saxony (German: Adalbert II. von Sachsen) (8 May 1467 - 1 May 1484) was the Administrator of Mainz from 1482 until 1484.

Adalbert was born in Meissen as a son of Duke Ernest of Saxony. Due to Adalbert's family being powerful in Thuringia, underage in August 1477 Adalbert was made the governor of the city of Erfurt by Archbishop Theodoric of Isenburg-Büdingen. In 1479 he was made a member of the cathedral of Mainz, and in 1480 was made Theodoric's coadjutor and successor. In 1481, despite his doubts, Pope Sixtus IV confirmed the appointment. After Theodoric died in 1482 Adalbert succeeded him, but not as archbishop as he was not yet old enough. In 1484 Adalbert died, still too young, and is therefore not listed as an archbishop of Mainz. He was buried in Mainz Cathedral.

Preceded by:

Adalbert III of Saxony

Succeeded by:

Theodoric of Isenburg-Büdingen Administrator of Mainz
1482 - 1484
Berthold of Henneberg-Aschach-Römhild