The House of Habsburg ( /ˈhæps.bɜrɡ/; German pronunciation: [ˈhaːps.bʊʁk]), also Hapsburg, and also known as House of Austria is one of the most important royal houses of Europe and is best known for being an origin of all of the formally elected Holy Roman Emperors between 1438 and 1740, as well as rulers of the Austrian Empire and Spanish Empire and several other countries.

The House takes its name from Habsburg Castle, a fortress built around 1020–1030 AD in present day Switzerland by Count Radbot of Klettgau, who chose to name his fortress Habsburg. His grandson, Otto II, was the first to take the fortress name as his own, adding "von Habsburg" to his title. The House of Habsburg gathered dynastic momentum through the 11th, 12th and 13th centuries. By 1276, Count Radbot's seventh generation descendant, Rudolph of Habsburg, had moved the family's power base from Habsburg Castle to the Archduchy of Austria. Rudolph had become King of Germany/Holy Roman Emperor in 1273, but the dynasty of the House of Habsburg was truly entrenched in 1276 when Rudolph became sovereign ruler of Austria, which the Habsburgs ruled for the next six centuries.

Otto von Habsburg (20 November 1912 – 4 July 2011), also known by his royal name as Archduke Otto of Austria, was the last Crown Prince of Austria-Hungary from 1916 until the dissolution of the empire in 1918, a realm which comprised modern-day Austria, Hungary, Bosnia and Herzegovina, Croatia, the Czech Republic, Slovakia, Slovenia, and parts of Italy, Montenegro, Poland, Romania, Serbia and Ukraine. He remained the Crown Prince of Hungary until also the deposition of the Habsburgs in Hungary in 1921. He subsequently became the pretender to the former thrones, Head of the Imperial House of Habsburg, and Sovereign of the Order of the Golden Fleece in 1922. He resigned as Sovereign of the Golden Fleece in 2000 and as head of the Imperial House in 2007.

The eldest son of Charles I, the last Emperor of Austria and King of Hungary, and his wife, Zita of Bourbon-Parma, Otto was born as third in line to the thrones, as His Imperial and Royal Highness Archduke and Prince Imperial Otto of Austria, Prince Royal of Hungary, Croatia and Bohemia. With his father's accession to the thrones in 1916, he was himself likely to become the Emperor. As his father never abdicated, Otto was considered by himself, his family and Austro-Hungarian legitimists to be the rightful Emperor-King from 1922.

Georg von Habsburg (given names Paul Georg Maria Joseph Dominikus; born 16 December 1964, Starnberg), referred to in Austria as Georg Habsburg-Lothringen, in Hungary as Habsburg György, and by his royal name as Archduke Georg of Austria, is the second son, and seventh and youngest child of Otto von Habsburg, the last Crown Prince of Austria-Hungary, and Princess Regina of Saxe-Meiningen.

He married Eilika Helene Jutta Clementine of Oldenburg (b. 22 August 1972) the older daughter of Duke Johann of Oldenburg (younger son of Nikolaus, Hereditary Grand Duke of Oldenburg and his wife Princess Helena of Waldeck and Pyrmont) and Countess Ilka of Ortenburg, on 18 October 1997 in Budapest, Hungary, the only one out of his siblings to make a dynastically equal marriage according to the Habsburg family laws. Had his father not accepted his older brother's marriage to Baroness Francesca Thyssen-Bornemisza, which would have been otherwise considered morganatic, Georg would have been his father's heir after his elder brother, as it would have been with Archduke Franz-Ferdinand towards Emperor Franz-Joseph. His wife remained Lutheran. The couple has three children:

 Johann Michael Haydn (help·info) (14 September 1737 – 10 August 1806) was an Austrian composer of the classical period, the younger brother of Joseph Haydn.

Johann Michael Haydn was born in 1737 in the Austrian village of Rohrau, Austria near the Hungarian border. His father was Mathias Haydn, a wheelwright who also served as "Marktrichter", an office akin to village mayor. Haydn's mother Maria, née Koller, had previously worked as a cook in the palace of Count Harrach, the presiding aristocrat of Rohrau. Mathias was an enthusiastic folk musician, who during the journeyman period of his career had taught himself to play the harp, and he also made sure that his children learned to sing; for details see Mathias Haydn.

Michael's early professional career path was paved by his older brother Joseph, whose skillful singing had landed him a position as a boy soprano in the St. Stephen's Cathedral, Vienna where he worked as a chorister, under the direction of Georg Reutter. Other singers in that choir included Johann Georg Albrechtsberger and Franz Joseph Aumann, both composers with whom Haydn later traded manuscripts. The early 19th century author Albert Christoph Dies, reporting from Joseph's late-life reminiscences, says the following:

Karl von Habsburg (Karl Thomas Robert Maria Franziskus Georg Bahnam; born 11 January 1961), referred to in Austria as Karl Habsburg-Lothringen, in France as Charles de Habsbourg-Lorraine, in the Czech Republic as Karel Habsbursko-Lotrinský, in Hungary as Habsburg Károly, and by his royal name as Archduke Karl of Austria, or, by monarchists, Karl II of Austria or Károly V of Hungary, is an Austrian politician, and the current Head of the House of Habsburg, and the Grand Master of the Order of the Golden Fleece. Born in Starnberg, Bavaria, Germany, he is the son of Otto von Habsburg and Princess Regina of Saxe-Meiningen, and the grandson of the last Austrian emperor, Charles I. He served as a Member of the European Parliament for the Austrian People's Party 1996–1999.

Since 1986, Karl von Habsburg has been president of the Austrian branch of the Paneuropean Union. After studying law for 12 years, in 1992/1993, he had a TV game show with Austrian public TV broadcaster ORF, called Who is Who. In October 1996, he was elected to the European Parliament for the Austrian People's Party (ÖVP). Two years later, it emerged that the ÖVP's election campaign had benefitted from 30,000 euros of World Vision donation money via Paneurope Austria while Karl von Habsburg sat on the board of World Vision Austria, apparently without noticing the director's dubious activities.