Alyssa Whitall Pearsall Smith (21 July 1867 – 22 January 1951) was the first wife of Bertrand Russell.
Born in Philadelphia, Pennsylvania, she was the daughter of Robert Pearsall Smith and Hannah Whitall Smith, prominent figures in the Holiness movement in America and the Higher Life movement in Great Britain. She was the sister of essayist and critic Logan Pearsall Smith and the cousin of Martha Carey Thomas.
Her family lived in England from 1873 to 1875 and then again from 1888 onward. In England the family came into contact with George Bernard Shaw, Henry James, and Bernard Berenson, who married her sister Mary.
Alys married Bertrand Russell on 13 December 1894 in the Quaker Meeting House in St. Martin's Lane, London, England. They separated in 1911 and divorced in 1921.
She chaired the Italian Refugees' Relief Committee to help people fleeing Benito Mussolini's Italy.