Rabbi Yisroel Hopstein was born around 1736-1737 in Opatow (Apta), Poland, to Shabtai, a poor bookbinder, and Perl. According to tradition, his birth came after his parents, poor and advanced in age, received a blessing from the Baal Shem Tov. Though physically frail, he was recognized early on as a prodigy.

He first attached himself to Rabbi Shmelke of Nikolsburg, who persuaded him to travel to Mezritch to the Maggid, Rabbi Dov Ber. After the Maggid's passing he became a disciple of Rabbi Elimelech of Lizhensk. He said that he had studied some eight hundred works of Kabbalah before coming to the Maggid of Mezritch, and Rabbi Chaim of Volozhin attested to the breadth of his Torah knowledge.

After teaching children in Przysucha, he settled in Kozienice (Kozhnitz) and became its preacher, hence the name "Maggid of Kozhnitz". After the passing of his teacher in Lizhensk he led a Chassidic court there, to which thousands, including non-Jews, flocked for his blessings, especially for healing. Ill and bedridden for much of his life, he would rally his strength when the time for prayer came, praying and dancing like a young man. He also worked to publish the writings of the Maharal of Prague.

His many disciples included Rabbi Yitzchak Meir of Ger, the Holy Jew of Przysucha, Rabbi Simcha Bunim of Przysucha, Rabbi Shalom Rokeach of Belz and Rabbi Naftali of Ropshitz. His works include Avodat Yisrael on the Torah and Pirkei Avot, his best-known book; Geulat Yisrael on the writings of the Maharal; Nezer Yisrael on the Zohar; Or Yisrael on the Tikkunei Zohar; Tehillot Yisrael on Psalms; and Beit Yisrael on the Talmud.

He married Royze, and their children were Rabbi Moshe Elyakim Beriah, who succeeded him, Leah Perl, and Mottel, who died young. He passed away in Kozienice on 14 Tishrei 5575 (September 28, 1814), and an ohel stands over his grave.