Karl von Harrach (1570 – 16 May 1628) was a Holy Roman nobleman, statesman and diplomat. Over the course of his career he became involved in the internal power struggle over the Holy Roman crown. In 1627, he received the Spanish version of the Order of the Golden Fleece.
Harrach was born in 1570: he was the second child of Leonhard IV Graf von Harrach and Maria Jacobea Gräfin Hohenzollern. In 1590, he bore the flag of Charles II at his funeral. He served as the chamberlain of Archduke Ernest of Austria. On 11 August 1595, he was appointed by emperor Rudolf II to the Lower Austrian Regimentsrathe. At the time of an internal power struggle between Rudolf and his brothers, he used his position in the Imperial Court to supply Ferdinand II (who resided in Graz) with vital information about the other pretenders to the Imperial crown. In 1601, he was appointed to the position of Imperial chamberlain. In 1608, he played an instrumental role in Matthias's seizure of the titles of Archduke of Austria, King of Croatia and King of Hungary. From 1614 until 1617, he served as an imperial ambassador in various states within the empire. On 26 September 1617, he became the cosignatory of the Treaty of Madrid (1617) along with Venetian ambassadors Giustiniani and Contarini, the treaty officially ended the Uskok War between the two states. In 1620, he was sent as an Imperial envoy to the court of Maximilian I, Elector of Bavaria. He then became a member of emperor Ferdinand's Geheimrat (Privy Council), he joined the "Spanish faction" of the council centered around Hans Ulrich von Eggenberg.
In January 1625, his castle Schloss Pruggin Bruck an der Leitha was exempt from provincial taxation. On 25 August, he was granted the right to establish a private mint which he operated together with House of Liechtenstein. In 1627, Philip IV of Spain awarded him the Order of the Golden Fleece. On 16 May 1628, Harrach died in Prague, his body was subsequently transported to the Harrach family mausoleum located in the Augustinian Church, Vienna.
His marriage to Maria Elisabeth Freiin von Schrattenbach the daughter of Eggeberg, produced 6 sons and 3 daughters. His sons Johann Karl and Max served in the Imperial army and were killed in action during the course of the Thirty Years' War, dying unmarried. Ernst Adalbert (born 1598) became the Archbishop of Prague, heading the recatholicization in Bohemia. Franz Albrecht served as a diplomat, his marriage to Anna Magdalena Freiin von Jörgen produced no children. Leonhard and Otto Friedrich were the founders of two lines of succession. His eldest daughter was married to count Max von Waldstein cousin of Albrecht Wallenstein. His two younger daughters Elisabeth and Maximiliana were married to Imperial Generalissimo Albrecht von Wallenstein and his comrade Adam Erdmann Trčka von Líparespectively. Harrach's death and Eggeberg's resignation negatively influenced Wallenstein's popularity within the Imperial court, facilitating an internal purge orchestrated by Wallenstein's opponents. Wallenstein and Trčka were both murdered during the purge's culmination the Eger Bloodbath.