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.Rantzau got the danish Order of the Elephant in 1580 by King Fredrick II.
of Denmark.
He was the great-uncle of Josias von Rantzau, Marshal of France.