Ernest of Isenburg-Grenzau (German: Ernst von Isenburg-Grenzau) was the Count of Isenburg-Grenzau from 1619 until 1664.

Ernest was the youngest son of Count Salentin VII and Antonia Wihelmina of Aremberg. He succeeded his elder brother Salentin VIII as count of Isenburg-Grenzau in 1619.

In 1625 Ernest married Caroline Ernestine of Aremberg. Ernest made his career in the service of the army of the Habsburgs, serving as a field captain in the Thirty Years' War in the Netherlands for the Spanish crown. Ernest spent little time in his lands, although in 1632 he led 30,000 soldiers to eradicate the Swedes in the Ahr and the Rhineland. Ernest was rewarded for his success with the highest honour of the Habsburgs, a medal of the Order of the Golden Fleece.

In 1636 he was appointed the governor-general of the Netherlands, and married Maria Anna of Hohenzollern-Hechingen; Caroline having died unexpectedly in 1630. Ernest died in 1664 as the last living member of the House of Lower Isenburg. In 1645 Ernest was appointed the Minister of Finance by the Habsburg emperor. After his death Lower Isenburg was annexed by the Archbishop of Trier. Ernest was buried with full honours in the Cathedral of St. Michael in Brussels, and a large msrble epitaph was erected on his grave.

Preceded by:


Succeeded by:

Salentin VIII Count of Isenburg-Grenzau
1619 - 1664
annexed to Trier