Dov Ber ben Avraham of Mezeritch (דֹב בּער פֿון מעזעריטש; died December 1772 OS), also known as the Maggid of Mezeritch or Mezeritcher Maggid, was a disciple of Rabbi Israel ben Eliezer (the Baal Shem Tov), the founder of Hasidic Judaism, and was chosen as his successor to lead the early movement. Dov Ber is regarded as the first systematic exponent of the mystical philosophy underlying the teachings of the Baal Shem Tov, and through his teaching and leadership, the main architect of the movement. He established his base in Mezhirichi (in Volhynia), which moved the centre of Hasidism from Medzhybizh (in Podolia), where he focused his attention on raising a close circle of disciples to spread the movement. After his death the third generation of leadership took their different interpretations and disseminated across appointed regions of Eastern Europe, rapidly spreading Hasidism beyond Ukraine, to Poland, Galicia and Russia.
His teachings appear in Magid Devarav L'Yaakov, Or Torah, Likutim Yekarim, Or Ha'emet, Kitvei Kodesh, Shemuah Tovah, and in the works authored by his disciples. His inner circle of disciples, known as the Chevraia Kadisha ("Holy Brotherhood"), included Rabbis Avraham HaMalach (his son), Nachum of Czernobyl, Elimelech of Lizhensk, Zusha of Hanipol, Levi Yitzchok of Berditchev, Boruch of Medzhybizh, Aharon (HaGadol) of Karlin, Chaim Chaykl of Amdur, Menachem Mendel of Vitebsk, Shmuel Shmelke of Nikolsburg, Shlomo Flam (the Lutzker Maggid) and Shneur Zalman of Liadi.
The most common transliterations are Dov-Ber, Dov Baer and DovBer; rarely used forms are Dob Ber or Dobh Ber, which often depend on the region in Eastern Europe where Jews resided and hence the influence of the local Yiddish dialects. The name דוב-בער Dov-Ber is traceable back to the דב, and בער. It is thus an example of a bilingual tautological name.
Dov Ber of Mezeritch was known as the Maggid—"Preacher" or literally "Sayer," one who preaches and admonishes to go in God's ways—of Mezritsh (The German form Meseritz is sometimes used instead of Mezeritch).