Saidai-ji (西大寺) or the "Great Western Temple" is a Buddhist temple in the city of Nara, Nara Prefecture, Japan. The temple was established in AD 765 as a counterpart to Tōdai-ji and it is the main temple of the Shingon Risshu (真言律宗) sect of Buddhism after the sect's founder, Eison, took over administration in 1238.

One building, the Aizen-dō, houses a statue of Aizen Myō-ō, while the main image is of Shakyamuni Buddha, erected by Eison in 1249.

Saidai-ji stands close to Yamato-Saidaiji Station on the Kintetsu Nara Line.