Percival "Percy" Dearmer (27 February 1867 – 29 May 1936) was an English priest and liturgist best known as the author of The Parson's Handbook, a liturgical manual for Anglican clergy. A lifelong socialist, he was an early advocate of the public ministry of women (but not their ordination to the priesthood) and concerned with social justice. Dearmer also had a strong influence on the music of the church and, with Ralph Vaughan Williams and Martin Shaw, is credited with the revival and spread of traditional and medieval English musical forms.
Born in Kilburn, Middlesex, to an artistic family—his father, Thomas Dearmer, was an artist and drawing instructor. Dearmer attended Streatham School and Westminster School (1880 – 1881), before going to a boarding school in Switzerland. From 1886 to 1889 he studied modern history at Christ Church, Oxford, receiving his Bachelor of Arts degree in 1890.
Dearmer was made a deacon in 1891 and ordained to the priesthood in 1892 at Rochester Cathedral. On 26 May of that year, he married 19-year-old Jessie Mabel Prichard White (1872 – 1915), the daughter of Surgeon-Major William White. She was a writer (known as Mabel Dearmer) of novels and plays. She died in 1915 while serving with an ambulance unit in Serbia during World War I. They had two sons, both of whom served in World War I. The elder, Geoffrey, lived to the age of 103, one of the oldest surviving war poets. The younger, Christopher, died in 1915 of wounds received in battle.
Dearmer's liturgical leanings were the product of a late Victorian debate among advocates of Ritualism in the Church of England. Although theoretically in agreement about a return to more Catholic forms of worship, high church clergy argued over whether these forms should be appropriated from post-Tridentine Roman Catholic practices or revived from the traditions of a pre-Reformation "English Use" rite. Dearmer's views fell very much on the side of the latter.