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.

Born Maria Teresa, and named after her maternal grandmother Maria Theresa of Austria, she was the eldest of 17 children born to her parents, the King and Queen of Naples and Sicily. Her father was a son of Charles III of Spain and Princess Maria Amalia of Saxony. Through her mother she was a niece of Marie Antoinette; through her father she was a niece of Maria Luisa of Spain and Charles IV of Spain. She was her mother’s favourite child from birth until she left the Neapolitan court to marry.
Her brothers included the future King Francis and Leopold, Prince of Salerno. Another, Carlo, Duke of Calabria died in 1778 aged 3 of smallpox.
Her sisters included Grand Duchess of Tuscany. Her younger sister Princess Maria Cristina, was the wife of the future Charles Felix of Sardinia as Queen of Sardinia. Maria Cristina’s twin Princess Maria Cristina Amelia died in 1783 of smallpox. Another sister was the Queen of the French as the wife of Louis Philippe I and the youngest was the future Princess of Asturias.

On 15 September 1790 she married her double first cousin Archduke Francis of Austria, who would later become Holy Roman Emperor Francis II, and then Emperor Francis I of Austria. The marriage is described as a happy one, despite differences in personality.
Maria Theresa was described as easy-going with a sensuous appearance. She loved masquerades and carnivals, and participated in every ball even while she was pregnant.

She did have some political influence, as she was interested in politics. She gave her husband advice and is believed to have been partially responsible for the dismissal of Johann Baptist Freiherr von Schloissnigg and Graf Franz Colloredo; she was also critical of Napoleon and encouraged her husband in the wars against him.
An important patron of Viennese music, she commissioned many compositions for official and private use. Joseph Haydn wrote his Te Deum for chorus and orchestra at her request. He also composed numerous masses to celebrate her reign. Her favourite composers included Paul Wranitzky and Joseph Leopold Eybler, a composer of sacred music.