Rabbi Elazar ben Arach was a Tanna of the second generation, in the first century, and one of the five great disciples of Rabban Yochanan ben Zakkai, together with Rabbi Eliezer ben Hurkanos, Rabbi Yehoshua ben Chananya, Rabbi Yosei HaKohen and Rabbi Shimon ben Netanel. Some regard him as the greatest of them. He lived in Jerusalem and, around the time of the destruction of the Second Temple, moved to Emmaus.

His teacher described him as an "ever-flowing spring", and Abba Shaul reported in his name: if all the sages of Israel were on one side of the scale, with Rabbi Eliezer ben Hurkanos among them, and Elazar ben Arach on the other, he would outweigh them all. The Talmud relates that he expounded the Maaseh Merkavah before Rabban Yochanan, who dismounted from his donkey, wrapped himself and sat down to listen. According to one opinion in the Talmud, the Tanna known as Rabbi Nehorai is in fact Rabbi Elazar ben Arach, so called because he enlightened the eyes of the sages in Torah.

In Pirkei Avot, when his teacher asked which is the good path a person should cleave to, he answered "a good heart", and the evil path to avoid, "an evil heart". He also taught: "Be diligent in the study of Torah; know what to answer a heretic; know before whom you toil, and that your employer can be trusted to pay you the reward of your labor."

According to the Talmud and Midrash, after his teacher's death he did not join the academy at Yavneh but, on his wife's advice, settled in Emmaus, known for its fine waters, expecting his colleagues to come to him. They did not, and he forgot his learning. When he came to read the verse "HaChodesh hazeh lachem", he read "HaCharash haya libam". The sages prayed for him and his learning returned.

His burial place is not mentioned in Talmudic literature. Since Benjamin of Tudela (around 1170) his tomb has been venerated at Alma in the Upper Galilee; other traditions place it near Dalton, in Safed or in Tiberias.