Karl I (30 July 1569 – 12 February 1627) was the first member of the House of Liechtenstein to become Prince of the Holy Roman Empire, but only as an honorary title, since the Liechtenstein family did not yet possess any territory with semi-sovereignty (Landeshoheit) within the Holy Roman Empire. (The territory of Liechtenstein was first purchased in 1699 and 1712 and declared a principality in 1719, whereby the princes became the monarchs of Liechtenstein.)
Karl was the elder son of Hartmann II, Baron of Liechtenstein and his wife, Countess Anna Maria of Ortenburg. Emperor Rudolf II of the Holy Roman Empire appointed Karl as chief intendant (Obersthofmeister), an important position at his court. Karl held this position until 1607. He became a Catholic in 1599.
In a dispute over land between Rudolf II and the heir presumptive to the throne, Archduke Matthias, Karl sided with Matthias. Liechtenstein played a leading role as adviser and supporter of Matthias in the coup against Emperor Rudolf II. Now-Hungarian King Matthias made him a hereditary prince in 1608, in thanks for Karl's aid. In his politics and assertiveness as advisor to Matthias, he rivaled Melchior Khlesl, Bishop of Vienna, who ultimately prevailed over Karl of Liechtenstein and became the new minister-favourite of King and later Emperor Matthias.