Shimon bar Yochai (Zoharic Aramaic: שמעון בר יוחאי, Shim'on bar Yoḥai) or Shimon ben Yochai (Mishnaic Hebrew: שמעון בן יוחאי, Shim'on ben Yoḥai), also known by the acronym Rashbi, was a 2nd-century tannaitic sage in ancient Judea, said to be active after the destruction of the Second Temple in 70 CE. He was one of the most eminent disciples of Rabbi Akiva. The Zohar, a 13th century foundational work of Kabbalah, is ascribed to him by Kabbalistic tradition.
In addition, the important legal works called Sifre and Mekhilta are attributed to him (not to be confused with the Mekhilta of Rabbi Ishmael, of which much of the text is the same). In the Mishnah, where he is the fourth-most mentioned sage, he is referred to as simply "Rabbi Shimon" (except Hagigah 1:7). In the baraita, midrash and gemara his name occurs either as Shimon or as Shimon ben Yochai.
According to modern legend, he and his son, Eleazar ben Simeon, were noted kabbalists. Both figures are held in unique reverence by kabbalistic tradition. By tradition they were buried in the same tomb in Meron, Israel, which is visited by thousands year round.
Shimon was born in Galilee. He was one of the principal pupils of Akiva, under whom he studied 13 years at Bnei Brak.
Berakhot 28a relates that Shimon had previously studied at Yavne, under Gamaliel II and Joshua ben Hananiah, and that he was the cause of the infamous quarrel that broke out between these two leaders. However, this statement is somewhat chronologically difficult, considering that about forty-five years later, when Akiva was thrown into prison, Shimon's father was still alive. Zecharias Frankel thus concluded the account in Berakhot 28a is spurious.
Shimon's acuteness was tested and recognized by Akiva when he first came to him; of all his pupils Akiva ordained only Meir and Shimon. Conscious of his own merit, Shimon felt hurt at being ranked after Meir, and Akiva was compelled to soothe him with soft words. During Akiva's lifetime Shimon was found occasionally at Sidon, where he seems to have shown great independence in his halakhic decisions.