Sophia Dorothea was born on 15 September 1666, the only child of George William, Duke of Brunswick- Lüneburg by his long-term mistress, Eleonore d’Esmier d’Olbreuse, Countess of Williamsburg, a Huguenot lady, the daughter of Alexander II d’Esmiers, Marquess of Olbreuse. Sophia Dorothea was legitimized at the age of eight, George William eventually married Eleonore officially in 1676. She had an average education for the time, she could read write and embroider well. There was some talk of marriage between Sophia Dorothea and the (then) future king of Denmark, but the reigning queen was talked out of it. Another engagement, to the Duke of Brunswick- Wolfenbüttel, was broken off, on the day the engagement was to be announced.