Question: Maria Theresa of Naples and Sicily, was the last Holy Roman Empress and the first Empress of Austria by marriage to who, that was the last Holy Roman Emperor, ruling from 1792 until 6 August 1806, when he dissolved the Holy Roman Empire of the German Nation after the decisive defeat at the hands of the First French Empire led by Napoleon at the Battle of Austerlitz?
Context: Maria Theresa of Naples and Sicily (6 June 1772 – 13 April 1807) was the last Holy Roman Empress and the first Empress of Austria by marriage to Francis II, Holy Roman Emperor.  She was the eldest daughter of Ferdinand IV & III of Naples and Sicily (later Ferdinand I of the Two Sicilies) (1751–1825) and his wife, Marie Caroline of Austria (1752–1814). Elisabeth Christine of Brunswick-Wolfenbüttel (28 August 1691 – 21 December 1750) was Princess of Brunswick-Wolfenbüttel, Holy Roman Empress, German Queen, Queen of Bohemia and Hungary; and Archduchess of Austria by her marriage to Emperor Charles VI.  She was renowned for her delicate beauty and also for being the mother of Empress Maria Theresa.  She was the longest serving Holy Roman Empress. Archduke Maximilian Francis of Austria (full German name: Maximilian Franz Xaver Joseph Johann Anton de Paula Wenzel von Österreich, 8 December 1756 in Vienna – 26 July 1801 in Vienna) was Archbishop and Elector Spiritual of Cologne (and as such Chancellor of the Holy Roman Empire for Italy), and Grand Master of the Teutonic Knights.  He was the youngest child of the Habsburg ruler of Austria, Maria Theresa, and her husband, Francis I, Holy Roman Emperor, for whom he was named.  His siblings included Holy Roman Emperors Joseph II and Leopold II, Maria Carolina, Queen of Naples and Sicily, and Marie Antoinette, Queen of France and Navarre.  He was the last fully functioning Elector of Cologne and was the employer and patron of the young Ludwig van Beethoven. Adelaide of Italy (93116 December 999), also called Adelaide of Burgundy, was a Holy Roman Empress by marriage to Holy Roman Emperor Otto the Great; she was crowned as the Holy Roman Empress with him by Pope John XII in Rome on February 2, 962.  She was regent of the Holy Roman Empire as the guardian of her grandson in 991-995. The Duchy of Württemberg (German: "Herzogtum Württemberg" ) was a duchy located in the south-western part of the Holy Roman Empire.  It was a member of the Holy Roman Empire from 1495 to 1806.  The dukedom's long survival for nearly four centuries was mainly due to its size, being larger than its immediate neighbors.  During the Protestant Reformation, Württemberg faced great pressure from the Holy Roman Empire to remain a member.  Württemberg resisted repeated French invasions in the 17th and 18th centuries.  Württemberg was directly in the path of French and Austrian armies who were engaged in the long rivalry between the House of Bourbon and the House of Habsburg.  In 1803, Napoleon raised the duchy to be the Electorate of Württemberg of the Holy Roman Empire, and when he abolished the Empire in 1806, the Electorate was elevated as the Kingdom of Württemberg. Holy Roman Empress or Empress of the Holy Roman Empire is the title given to the consort (wife) or regent of the Holy Roman Emperor.  The elective dignity of Holy Roman Emperor was restricted to males only, therefore there was never a Holy Roman Empress regnant, though women such as Theophanu or Maria Theresa of Austria, who controlled the power of rule, served as de facto Empresses regnant. The Josephinian Land Survey (German: "Josephinische Landesaufnahme" ) was the first comprehensive land survey and mapping of the Habsburg Empire.  The survey was ordered by Holy Roman Empress Maria Theresa after Austria's defeat in the Seven Years' War.  It was conducted from 1763 to 1787, concluding in the reign of Holy Roman Emperor Joseph II.  The maps are currently stored in the National Archives of Austria. Maria Amalia of Austria (26 February 1746 – 18 June 1804) was the Duchess of Parma, Piacenza and Guastalla by marriage.  Maria Amalia was a daughter of Empress Maria Theresa and Emperor Francis I.  She was thus younger sister to Joseph II, Holy Roman Emperor and older sister to Leopold II, Holy Roman Emperor, Maria Carolina, Queen of Naples and Marie Antoinette, Queen of France. The monarchs of Prussia were members of the House of Hohenzollern who were the hereditary rulers of the former German state of Prussia from its founding in 1525 as the Duchy of Prussia.  The Duchy had evolved out of the Teutonic Order, a Roman Catholic crusader state and theocracy located along the eastern coast of the Baltic Sea.  The Teutonic Knights were under the leadership of a Grand Master, the last of whom, Albert, converted to Protestantism and secularized the lands, which then became the Duchy of Prussia.  The Duchy was initially a vassal of the Kingdom of Poland, as a result of the terms of the Prussian Homage whereby Albert was granted the Duchy as part of the terms of peace following the Prussian War.  When the main line of Prussian Hohenzollerns died out in 1618, the Duchy passed to a different branch of the family, who also reigned as Electors of Brandenburg in the Holy Roman Empire.  While still nominally two different territories, Prussia under the suzerainty of Poland and Brandenburg under the suzerainty of the Holy Roman Empire, the two states are known together historiographically as Brandenburg-Prussia.  Following the Second Northern War, a series of treaties freed the Duchy of Prussia from any vassalage to any other state, making it a fully sovereign Duchy in its own right.  This complex situation (where the Hohenzollern ruler of the independent Duchy of Prussia was also a subject of the Holy Roman Emperor as Elector of Brandenburg) laid the eventual groundwork for the establishment of the Kingdom of Prussia in 1701.  For diplomatic reasons, the rulers of the state were known as the King in Prussia from 1701 to 1772; largely because they still owed fealty to the Emperor as Electors of Brandenburg, the "King in Prussia" title (as opposed to "King of Prussia") avoided offending the Emperor.  As the Prussian state grew through several wars and diplomatic moves throughout the 18th century, it became apparent that Prussia had become a Great Power that did not need to submit meekly to the Holy Roman Empire.  By 1772, the pretense was dropped, and the style "King of Prussia" was adopted.  Thus it remained until 1871, when in the aftermath of the Franco-Prussian War, the King of Prussia Wilhelm I was crowned German Emperor.  From that point forward, though the Kingdom of Prussia retained its status as a constituent state of the German Empire, all remaining Kings of Prussia also served as German Emperor, and that title took precedence. Francis II (German: "Franz" ; 12 February 1768 – 2 March 1835) was the last Holy Roman Emperor, ruling from 1792 until 6 August 1806, when he dissolved the Holy Roman Empire of the German Nation after the decisive defeat at the hands of the First French Empire led by Napoleon at the Battle of Austerlitz.  In 1804, he had founded the Austrian Empire and became Francis I, the first Emperor of Austria, ruling from 1804 to 1835, so later he was named the one and only "Doppelkaiser" (double emperor) in history.
Answer: Francis II, Holy Roman Emperor