Heinrich Rantzau or Ranzow (Ranzovius) (11 March 1526 – 31 December 1598) was a German humanist writer and statesman, a prolific astrologer and an associate of Tycho Brahe. He was son of Johan Rantzau. He was Governor of the Danish royal share in the Duchy of Holstein, a rich man and celebrated book collector. Rantzau is perhaps best remembered as a patron of scholars. His own Tractatus astrologicus de genethliacorum thematum appeared in 1597, and went through five editions by 1615. In his own time, he was regarded as a generous supporter of artists and writers in Lübeck, many of whom he engaged to write memorials of his father. Rantzau was also a successful merchant with trading interests in the east-west trade through Husum and Lübeck.
Felgentreu, Fritz (ed., trans.). Heinrich Rantzau (Christianus Cilicius Cimber). Belli Dithmarsici vera descriptio: Wahre Beschreibung des Dithmarscher Krieges (Schleswig: Landesarchiv Schleswig-Holstein, 2009) (Veröffentlichungen des Landesarchivs Schleswig-Holstein, 86).