Agnes Mary Clerke (10 February 1842 – 20 January 1907) was an astronomer and writer, mainly in the field of astronomy. She was born in Skibbereen, County Cork, Ireland, and died in London.
Agnes Clerke was the daughter of John William Clerke (ca. 1814–1890) and his wife Catherine Mary Deasy (b. ca. 1819). Her father was a judge's registrar. She had two siblings; her older sister, Ellen Mary, was born in 1840, and her younger brother, Aubrey St. John, was born in 1843. All of the Clerke children were entirely home schooled.
She was interested in astronomy from an early age, and had begun to write about it before the age of 15. In 1861 her family moved to Dublin, and in 1863 to Queenstown. Several years later she went to Italy where she stayed until 1877, chiefly at Florence, studying at the public library and preparing for literary work. In 1877 she settled in London.
Her first important article, Copernicus in Italy, was published in the Edinburgh Review in October 1877. She achieved a worldwide reputation in 1885, on the appearance of her exhaustive treatise, A Popular History of Astronomy during the Nineteenth Century. Clerke was not a practical astronomer, instead collating, interpreting and summarising the results of astronomical research. In 1888 she spent three months at the Cape Observatory as the guest of the director, Sir David Gill, and his wife, and there became sufficiently familiar with spectroscopic work to be able to write about this newer branch of the science with increased clearness and confidence.
In 1892 she was awarded the Actonian Prize of 100 guineas by the Royal Institution. As a member of the British Astronomical Association she attended its meetings regularly, as well as those of the Royal Astronomical Society. In 1903, with Lady Huggins, she was elected an honorary member of the Royal Astronomical Society, a rank previously held only by two other women, Caroline Herschel and Mary Somerville.
Her sister, Ellen Mary Clerke (1840–1906), also wrote about astronomy.
The lunar crater Clerke is named after her.