Later in life, she would claim that she was born on 25 December 1785, a fabrication she maintained to such an extent that even on her death certificate there is no certainty about her age, stating that she was "about 80 years".

[1] Sydney spent the earliest years of her childhood at the Owensons' home at 60 Dame Street in Dublin with her mother Jane and sister Olivia.

Sydney was primarily educated by her mother, but she also received tutoring from a young boy named Thomas Dermody, a local prodigy whom their father had rescued from poverty.

Sydney spent three years at a Huguenot academy at Clontarf and then attended a finishing school in Earl Street, Dublin.

She collected Irish tunes, for which she composed the words, thus setting a fashion adopted with signal success by Thomas Moore.

[2] Her novel St. Clair (1804), about ill-judged marriage, ill-starred love and impassioned nature worship, in which the influence of Johann Wolfgang von Goethe (specifically his novel The Sorrows of Young Werther)[2] and Jean-Jacques Rousseau was apparent, at once attracted attention.

[6] Miss Owenson entered the household of John Hamilton, 1st Marquess of Abercorn, and in 1812 — persuaded by Lady Abercorn, the former Lady Anne Jane Gore — she married the philosopher and surgeon to the household, Sir Thomas Charles Morgan, but books continued to flow from her facile pen.

Her elaborate study (1817) of France under the Bourbon Restoration was attacked with outrageous fury by John Wilson Croker in the Quarterly Review, the author being accused of Jacobinism, falsehood, licentiousness, and impiety.

[7] Her heroines were violently removed from what Croker considered their proper sphere as "a useful friend, a faithful wife, a tender mother, and a respectable and happy mistress of a family".

[8] Owenson took her revenge indirectly in the novel Florence Macarthy (1818) —translated into French by Jacques-Théodore Parisot—, in which a Quarterly reviewer, Con Crawley, is insulted with supreme feminine ingenuity.

It was proscribed by the King of Sardinia, the Emperor of Austria and the Pope, but Lord Byron bore testimony to the justness of its pictures of life.