Rabbi Elazar ben Azariah was a Tanna of the Yavneh generation, a contemporary of Rabban Gamliel, Rabbi Eliezer, Rabbi Yehoshua and Rabbi Akiva. A kohen, he was the tenth generation after Ezra the Scribe and was famed for his great wealth. His father, Rabbi Azariah, was likewise a wealthy and respected kohen, and his uncle was the Tanna Shimon, brother of Azariah. He studied under Rabbi Yosei HaGlili and later joined the sages of Yavneh.

When the sages of Yavneh decided to remove Rabban Gamliel from the presidency of the Sanhedrin, they chose Rabbi Elazar for his wisdom, lineage and wealth. According to the Babylonian Talmud he was only eighteen; he consulted his wife, who pointed out that he had no white hair, and eighteen rows of white hair miraculously grew on him. This is how the Talmud explains his saying in the Mishnah, recalled in the Passover Haggadah: "I am like a man of seventy." Under his presidency the doors of the study hall were opened to all, and hundreds of benches were added. Rabban Gamliel was later reinstated, but Rabbi Elazar continued to share the leadership with him, preaching one Shabbat in four (or in three).

He travelled to Rome with Rabban Gamliel, Rabbi Yehoshua and Rabbi Akiva, and often disputed with Rabbi Akiva. The principle "the Torah speaks in the language of people" is attributed to him, and he opposed frequent death sentences: in his view, a court that executes once in seventy years deserves to be called murderous. Pirkei Avot records in his name that where there is no bread, Torah cannot thrive, and without Torah there is no bread. His students included Rabbi Yehuda and Rabbi Meir.

When he died, the sages said that the crown of the sages had been removed. According to a tradition attested since the Middle Ages, he is buried at Alma in the Upper Galilee, near his father Rabbi Azariah.