Jane Elizabeth Harley (née Scott), Countess of Oxford and Countess Mortimer (1774–1824) was a notable English noblewoman, known as a patron of the Reform movement and a lover of Lord Byron.
She was a daughter of the Reverend James Scott, M.A., Vicar of Itchen Stoke in Hampshire and was brought up in favour of French Revolutionary thought and Reform. In 1794 she married Edward Harley, 5th Earl of Oxford and Earl Mortimer (with her father taking the service), being styled Countess of Oxford and Countess Mortimer. She was a friend of the Princess of Wales. She frequently took lovers from among the pro-Reform party during her marriage, firstly Francis Burdett and most notably Lord Byron (the affair lasting from 1812, in the aftermath of Byron's affair with Caroline Lamb, when he was fourteen years her junior, until 1813, when she and her husband went abroad but Byron did not follow as she had hoped). Her marriage was not a love match and her large number of children were known as the "Harleian Miscellany" due to uncertainties over whether her husband was their father, but the marriage did not break up.