The House of Windisch-Graetz, also spelled Windisch-Grätz, is an Austrian aristocratic family, descending from Windischgraz in Lower Styria (present-day Slovenj Gradec, Slovenia). The noble dynasty serving the House of Habsburg achieved the rank of Freiherren in 1551, of Imperial Counts in 1682 and of Princes of the Holy Roman Empire in 1804.
According to the Almanach de Gotha, the family was first recorded in 1242. They temporarily served as ministeriales of the Patriarchs of Aquileia. One Conrad of Windischgracz (d. 1339) acted as a Habsburg administrator in the Habsburg Duchy of Styria from 1323 onwards.
In 1574 the dynasty obtained Inkolat in Bohemia; later, however, several members converted to Protestantism and lost their estates in the course of the Thirty Years' War. The Austrian diplomate Count Gottlieb of Windisch-Graetz (1630–1695) again converted to Catholicism in 1682 and was elevated to a Reichsgraf by the Habsburg emperor Leopold I in the same year. In 1693 his son Ernst Friedrich (1670–1727) acquired Červená Lhota Castle in Southern Bohemia, which his descendant Joseph Nicholas of Windisch-Graetz (1744–1802) had to sell in 1755.
Count Alfred Candidus Ferdinand zu Windisch-Graetz (1787–1862) was elevated to the rank of Fürst (Prince) in 1804. After the Holy Roman Empire was abolished two years later, he and his brother Weriand were both created Princes of the Austrian Empire in 1822, with Alfred and his successors being the first line of Princes of Windisch-Graetz, and Weriand and his successors being the second line.