Fiona MacCarthy's excellent brief biography of William Morris is available in the Oxford Dictionary of National Biography (2004), requires log-in (article URL: http://www.oxforddnb.com/view/article/19322?docPos=3). MacCarthy is the author of the standard recent biography of Morris, William Morris: A Life for Our Time (1994), and her essay provides supplementary information on Morris’s artistic and political activities as well as his family and private life. Copyright restrictions prevent us from reproducing her entry here.
For those who may not have access to the ODNB, we here provide J. W. Mackail’s 1901 Dictionary of National Biography entry. Mackail was the Burne-Joneses’ son-in-law and Morris's first biographer, and his account offers a good discussion of Morris’s literary work and his character as viewed by his contemporaries.
J. W. Mackail, The Life of William Morris, 1899. vol. 1 & vol. 2