Friedrich IX von Brandenburg
- Category : Notable-Famous-Royal-family
- Type : MS
- Profile : 3/5 - Martyr / Heretic
- Definition : Single
- Incarnation Cross : RAX Tension 1
German nobility, a member of the house of Hohenzollern, and a Margrave of Brandenburg.
Frederick was a son of the Elector John George of Brandenburg (1525–1598) from his third marriage to Elisabeth (1563–1607), daughter of Prince Joachim Ernest of Anhalt. Frederick was educated in Frankfurt and Tübingen and undertook an extensive Grand Tour through Europe. In 1694, he was appointed Coadjutor and then, in 1610, elected Herrenmeister (literally, "Master of the Knights", equivalent to Grand Master) of the Order of Saint John, Bailiwick of Brandenburg, which was seated at Sonnenburg.
He died at the age of 23 on 19 May 1611 in Sonnenburg, Prussia (now Słońsk, Poland).