Michael Field was a pseudonym used for the poetry and verse drama of Katharine Harris Bradley (27 October 1846 – 26 September 1914) and her niece and ward Edith Emma Cooper (12 January 1862 – 13 December 1913). As Field they wrote around 40 works together, and a long journal Works and Days. Their intention was to keep the pen-name secret, but it became public knowledge, not long after they had confided in their friend Robert Browning.
Katharine Bradley was born on 27 October 1846 in Birmingham, England, the daughter of Charles Bradley, a tobacco manufacturer, and of Emma (née Harris). Her grandfather, also Charles Bradley (1785–1845), was a prominent follower and financial backer of prophetess Joanna Southcott and her self-styled successor John "Zion" Ward. She was educated at the Collège de France and Newnham College, Cambridge.
Bradley's elder sister, Emma, married James Robert Cooper in 1860, and went to live in Kenilworth, where their daughter, Edith Emma Cooper was born on 12 January 1862. Emma Cooper became an invalid for life after the birth of her second daughter, Amy, and Katharine Bradley, being her sister, stepped in to become the legal guardian of her niece Edith Cooper.
Bradley was for a time involved with Ruskin's utopian project. She published first under the pseudonym Arran Leigh, a nod to Elizabeth Barrett. Edith adopted the name Isla Leigh for their first joint publication, Bellerophôn.
From the late 1870s, when Edith was at University College, Bristol, they agreed to live together and were, over the next 40 years, lesbian lovers, and co-authors. Their first joint publication as Michael Field was "Callirhöe and Fair Rosamund" in 1884. They had financial independence: Bradley's father Charles Bradley had been in the tobacco industry in Birmingham.