The title of Archduke (feminine: Archduchess) (German: Erzherzog, feminine form: Erzherzogin) denotes a noble rank above Duke and below King, used only by princes of the Houses of Habsburg and Habsburg-Lorraine.

Territory ruled by an archduke or archduchess is called an archduchy.

As an archduke was a rank mostly reserved to the Habsburg imperial and royal family, the correct form of address was "Imperial and Royal Highness" but only after 1804 when the Austrian Empire was formed. This is usually considered a higher style than "Imperial Highness", a style reserved for descendants of an emperor and "Royal Highness", used to denote descent from a king. It is also, generally, the highest variation of the style "Highness".

The English word is recorded only since 1530, derived from Middle - via Old French archeduc, from Merovingian Latin archidux, from arch(i)- (see arch- (adj.)) + dux 'duke' .

Archduke (in German Erzherzog) is a title distinct from Grand duke (in German Großherzog), used in some other German royal houses and still in sovereign Luxembourg.

Gisela Louise Marie, Princess Imperial and Archduchess of Austria, Princess of Hungary and Bohemia, Princess of Bavaria (12 July 1856 – 27 July 1932) was the second daughter and eldest surviving child of Emperor Franz Joseph I of Austria and Empress Elisabeth. Her German title was Gisela Louise Marie, Erzherzogin von Österreich, Prinzessin von Bayern.

Although christened Gisella (with a double L) she only ever wrote her name with one L. She was named after a 10th century Habsburg ancestress. Just like her older sister and her brother, Gisela was raised by her paternal grandmother, Archduchess Sophie of Austria. She had a very close relationship with her younger brother, Crown Prince Rudolf, whose apparent suicide hit her hard.

Her father collected some the family's personal items, such as the first pair of shoes worn by each of his children. Among these keepsakes was a poem written for him by a young Gisela one Christmas - the poem was said to be the most treasured item among this collection. Archduchess Gisela was also known to paint in her later years.

Archduchess Marie Valerie of Austria (22 April 1868 – 6 September 1924) was the fourth and last child of Emperor Francis Joseph of Austria and Elisabeth of Bavaria ("Sisi"). Her given name was Marie Valerie Mathilde Amalie, but she was usually called Valerie.

Princess Marie Valerie was born at Ofen (Buda) in Hungary. The Empress Elisabeth was especially attached to Valerie, who was born ten years after the imperial couple's third child, and whom she was allowed to raise herself in contrast to her first three children who were taken from her in infancy and raised by the Emperor's mother, Archduchess Sophie. Sophie herself wrote to Elisabeth's mother Ludovika, "Sisi is completely absorbed by her love and care for this irresistible little angel."

She was Elisabeth's favorite child by far, and was acidly referred to by some courtiers as "Die Einzige" ("The Only Child") because Elisabeth paid so much more attention to her than her siblings. Valerie loved her mother, but according to her diaries, often felt embarrassed and overwhelmed by Elisabeth's concentration on her, particularly as she herself was of a modest and practical nature.

Sophie Friederike Dorothee Wilhelmine, Princess of Bavaria (27 January 1805 – 28 May 1872) was born to King Maximilian I Joseph of Bavaria and his second wife Karoline of Baden. She was the identical twin sister of Princess Maria Anna of Bavaria, Queen of Saxony as wife of Frederick Augustus II of Saxony. Her son Maximilian reigned as Emperor of Mexico.

On 4 November 1824, she married Franz Karl, Archduke of Austria. They had six children.

Her ambition to place her oldest son on the Austrian throne was a constant theme in Austrian politics. At the time she was called "the only man at court". During the Revolution of 1848, she persuaded her somewhat feeble-minded husband to give up his rights to the throne in favour of Franz Joseph, her son. After Franz Joseph's accession, Sophie became the power behind the throne. Within modern pop culture, Sophie is best remembered for her extremely bad relationship with Franz Joseph's famed wife Sisi, who was also her niece.

Sophie kept a detailed diary most of her life which reveals much about Austrian court life. She was deeply affected in 1867 by the execution in Mexico of her second son Maximilian. She never recovered from that shock, and withdrew from public life. She died of a brain tumor in 1872.

Archduchess Sophie of Austria (German: Sophie, Erzherzogin von Österreich; 5 March 1855 – 29 May 1857) was the first child and first of three daughters born to the Empress Elisabeth (Sisi) and Franz Joseph, Emperor of Austria. She died aged two.

Within two months of the marriage, Elisabeth was obviously pregnant. On 5 March 1855, the soon-to-be eighteen-year-old Empress of Austria delivered a daughter who was christened the same day Sophie Friederike Dorothea Maria Josepha, after Franz Joseph's mother. The infant was christened such without Elisabeth even knowing. On both her mother and her father's side, Sophie descended from King Maximilian I Joseph of Bavaria, as her parents were first cousins. On her father's side, she descended from the last Holy Roman Emperor, Francis II. During the next year, Elisabeth presented Franz Joseph with another daughter, Archduchess Gisela, a younger sister to Sophie. Even though they were both girls and did not need to be educated for duties a monarch would be obliged to fulfil, both infants right after being baptised were taken away from Elisabeth by Princess Sophie of Bavaria (who was both Elisabeth's aunt and mother-in-law) on account of the Empress being to young to raise two children. Elisabeth later commented: