Shmuel Shmelke HaLevi Horowitz of Nikolsburg (Yiddish: שמואל שמעלקי הלוי הורוויץ פון ניקאלשבורג, [ˈʃmɛlkɛ ˈfʊn ˈnɪkɛlʃbʊʁɡ]; 1726 – April 28, 1778) also known as the Rebbe Reb Shmelke was an early Hasidic master and kabbalist, who is amongst the most important figures to early Polish Hasidism.

A leading disciple of Dov Ber of Mezeritch, he held rabbinic positions in Rychwal and Sieniawa, where he successfully introduced Hasidic Judaism to the region.

From 1773 to 1778, he served as the Chief Rabbi of Moravia, basing himself in the town of Nikolsburg (Mikulov), where he introduced Hasidic philosophy to the chagrin of the city's conservative Misnagdic population.

He held this position for some time, during which several young Hassidim came to study with him from surrounding areas, the most notable of which being Yaakov Yitzchak of Lublin, Levi Yitzchok of Berditchev and Yisroel Hopstein.

In 1762, he authored his magnum opus, Divrei Shmuel which contained homiletic and kabbalistic commentaries on the Talmudic tractates Bava Batra and Orach Chayyim.

Abraham Trebitsch reported that on his first day as Chief Rabbi, Reb Shmelke began performing miracles, the most notable of which was bringing rain to Nikolsburg during a dry season.

Mid-way through his rabbinic carrier, Reb Shmelke became involved in a heated dispute with a wealthy and influential Jew of the town who began to rally people against him.

The magistrate responded, stating that he knew for a fact that Reb Shmelke was a pious man, as he often saw the Prophet Elijah lighting his candle and learning with him.

Despite this, the community remained unconvinced and as a last resort, Reb Shmelke asked Elimelech of Lizhensk to come to Nikolsburg and convince the townsmen not to depose him.

Thrilled to find a rabbi who embraced their beliefs, the community once again assembled in the local synagogue to hear Reb Elimelech speak.