Lag BaOmer (Hebrew: ל״ג בעומר‎), also Lag B'Omer, is a Jewish holiday celebrated on the 33rd day of the Counting of the Omer, which occurs on the 18th day of the Hebrew month of Iyar.

This day marks the hillula (celebration, interpreted by some as anniversary of death) of Rabbi Shimon bar Yochai, aMishnaic sage and leading disciple of Rabbi Akiva in the 2nd century, and the day on which he revealed the deepest secrets of kabbalah in the form of the Zohar (Book of Splendor), a landmark text of Jewish mysticism. This association has spawned several well-known customs and practices on Lag BaOmer, including the lighting of bonfires, pilgrimages to the tomb of Bar Yochai in the northern Israeli town of Meron, and various customs at the tomb itself.