Mary Theresa Vidal (née Johnson) (23 June 1815 – 19 November 1873) was a British–Australian writer described as Australia's first female novelist.

The poet William Johnson, who took the name of Cory in 1872, was a younger brother.

In 1845, Vidal's first book, Tales for the Bush, was published in Sydney, apparently intended as an instructive work for her servants.

She sometimes made use of her experiences in Australia, especially in Bengala, or Some Time Ago (1860).

She died in 1873 and was survived by her husband, six sons (including George William Vidal) and a daughter.