Electress Sophia of Hanover (born Sophia, Countess Palatine of Simmern; 14 October 1630 – 8 June 1714) was the youngest daughter of Frederick V, Elector Palatine, of the House of Wittelsbach, the "Winter King" of Bohemia, and Elizabeth Stuart. She is frequently referred to as the '''''Duchess Sophia,' particularly when the text is also discussing her niece and future daughter-in-law Princess Sophia.

Through the Act of Settlement 1701, an Act of the Westminster Parliament which sought to suspend the normal laws of inheritance to the English and Scots thrones, Sophia was declared the heiress presumptive to her first cousin once removed, Queen Anne of England, Scotland and Ireland (later Queen of Great Britain and Ireland). She would have acceded to Anne's crown, had she not died a few weeks before Anne did. On Sophia's death, her son George Louis, Elector of Hanover and Duke of Brunswick-Lüneburg, became heir apparent. On Queen Anne's death, he became King George I.

As the mother of George I, she is therefore the legislative linchpin ancestor of the House of Hanover line of succession to the British throne and their modern descendants of the House of Windsor. Her grandfather was James I & VI of England and Scotland and her uncle was Charles I of England and Scotland. As Electress, Sophia was the consort to Ernest Augustus, Elector of Hanover until his death in 1698.

Sophia was born in exile in The Hague (as a result of her father's defeat at the Battle of White Mountain) and was the youngest of five daughters of Frederick V, Elector Palatine and Elizabeth Stuart. She was brought up in Leiden until moving back to her mother's court at The Hague in 1641. Her mother later suggested she marry their neighbour, the exiled Charles II, but Sophia was not interested in marrying her first cousin, and went to live with her brother, Charles I Louis (the new Elector Palatine, who had recently been restored to his lands) in Herrenhausen in 1650.

Before her marriage, Sophia, as the daughter of Frederick V, Elector Palatine of the Rhine, was referred to as Sophie, Princess Palatine of the Rhine, or as Sophia of the Palatinate.

On 30 September 1658, she married Ernst August, Duke of Brunswick-Lüneburg, at Heidelberg, who in 1692 became the first Elector of Hanover. (Electors were princes who had the right to vote to elect the emperor of the Holy Roman Empire). Ernst August was a second cousin of Sophia's mother Elizabeth Stuart, as they were both great grandchildren of Christian III of Denmark.

Sophia became a friend and admirer of Gottfried Leibniz while he was a courtier to the House of Brunswick, from 1676 until his death in 1716. This friendship resulted in a substantial correspondence, published in the 19th century (Klopp 1973), that reveals Sophia to have been a woman of unusual intellectual ability and curiosity.

Sophia commissioned significant work on the Herrenhausen Gardens surrounding the palace at Herrenhausen, where she died.

Sophia plays an important role in British history and royal lineage. As a daughter of Elizabeth Stuart and grand-daughter of James I of England, VI of Scotland, she was the closest Protestant relative to William III (king of England and Scotland by marriage and by being the son of Princess Mary, daughter of Charles I), after his childless sister-in-law, Princess Anne. In 1701, the Act of Settlement made her heiress presumptive for the purpose of cutting off any claim by the Catholic James Francis Edward Stuart, who would otherwise have become James III, as well as denying the throne to many other Catholics who held a claim. The act restricts the British throne to the "Protestant heirs" of Sophia of Hanover who have never been Catholic and who have never married a Catholic. Presently there are almost 5,000 descendants of Sophia although not all are in the line of succession. The Sophia Naturalization Act 1705 granted the right of British nationality to Sophia's non-Catholic descendants (though this has been modified by subsequent laws).

The Crown, in the default of legitimate issue from both William III and Anne, was settled upon “the most excellent princess Sophia, electress and duchess-dowager of Hanover” and “the heirs of her body, being Protestant.” The key excerpt from the Settlement, naming Sophia as heiress presumptive reads:

Therefore for a further Provision of the Succession of the Crown in the Protestant Line We Your Majesties most dutifull and Loyall Subjects the Lords Spirituall and Temporall and Commons in this present Parliament assembled do beseech Your Majesty that it may be enacted and declared and be it enacted and declared by the Kings most Excellent Majesty by and with the Advice and Consent of the Lords Spirituall and Temporall and Comons in this present Parliament assembled and by the Authority of the same That the most Excellent Princess Sophia Electress and Dutchess Dowager of Hannover Daughter of the most Excellent Princess Elizabeth late Queen of Bohemia Daughter of our late Sovereign Lord King James the First of happy Memory be and is hereby declared to be the next in Succession in the Protestant Line to the Imperiall Crown and Dignity of the forsaid Realms of England France and Ireland with the Dominions and Territories thereunto belonging after His Majesty and the Princess Ann of Denmark and in Default of Issue of the said Princess Ann and of His Majesty respectively.

Although considerably older than Queen Anne, Sophia enjoyed much better health. In 1714, Sophia was walking in the gardens of Herrenhausen when she ran to shelter from a sudden downpour of rain and collapsed and died, aged 83. Upon Sophia's death, her eldest son Elector Georg Ludwig of Hanover became heir presumptive in her place, and weeks later succeeded Queen Anne as George I. Sophia's daughter Sophia Charlotte of Hanover (1668-1705) married Frederick I of Prussia, from whom the later Prussian kings and German emperors descend. The connection between the German emperors and the British royal family, which was renewed by several marriages in future generations, would become an issue during World War I.

Sophia had additional sons, none of whom had children. Those who reached adulthood were: *Friedrich August of Brunswick and Lunenburg, Imperial General, (1661-1691) *Maximilian Wilhelm of Brunswick and Lunenburg, field marshal in the Imperial Army, (1666-1726) *Karl Philipp of Brunswick and Lunenburg, colonel in the Imperial Army, (1669-1690) *Christian of Brunswick and Lunenburg, (1671-1703) *Ernst August II of Brunswick and Lunenburg, Duke of York and Albany, became bishop of Osnabrück (1674-1728)

*British monarchy *UK topics *Gottfried Leibniz

*Klopp, Onno, ed., 1973 (1873). Correspondenz von Leibniz mit der Prinzessin Sophie. Hildesheim: Georg Olms. In French.