Mírzá Músá (Persian: میرزا موسى; d. 1887) was the only full brother of Baháʼu'lláh, meaning that they shared the same mother and father.
He experienced the same imprisonment, exile, assaults, and degrading circumstances that were given to the small band of family members associated with Baháʼu'lláh and ʻAbdu'l-Bahá.
Mírzá Músá remained a loyal and faithful follower until he died.
Mírzá Músá had at least three children: Mirza Majdi'd-Din, Ali Rida, and a daughter.
Later, he supported Mírzá Muhammad ʻAlí, and after his death Shoghi Effendi called him "the most redoubtable adversary of ʻAbdu'l-Bahá".