Ethel Rosalie Ferrer McCaul (1867-1931) was a British nurse, author, and advocate for improvements in military medical practice and care.

Sometime prior to 1899, McCaul established a private nursing home in London, with a staff of 20. It was here that she likely became acquainted with Dr. Frederick Treves, surgeon to the young Duke of York (later George V). Treves was one of eight civilian surgeons recruited in 1899 to serve alongside those of the Royal Army Medical Corps in the Anglo-Boer War in South Africa. He took with him his own staff and transport, his own surgical instruments, and two theatre nurses: Ethel McCaul and Alice Tarr. McCaul distinguished herself as a front-line nurse, while at the same time becoming an outspoken critic of shortcomings in in British medical practices, and a crusader for improvements based in large part on the high quality of care that she observed in the Japanese military.

Among other things, McCaul advocated for the creation of an independent corps of Army nurses to replace the use of Reserve System, which often resulted in soldiers being cared for by untrained and inexperienced staff. She founded the Union Jack Club in London because "[w]hile officers had their clubs, servicemen below commissioned rank had nowhere reputable to stay with their families in the nation's capital. Miss McCaul was determined that they should have the opportunity to do this and see London and all its sights."

In 1904, McCaul undertook, by the sanction of Queen Alexandra, a special mission to Japan and Manchuria in order to obtain information about the workings of the Japanese Red Cross in the Far East. She kept a diary of her trip, which was published as Under the Care of the Japanese War Office (Cassell & Company, 1904).

In 1914 she offered the British military the use of her nursing home, and it became the McCaul Hospital for Officers. Among its innovations was the use of a "Colour Ward," which employed "positive" hues such as warm yellow, spring green, and blue to soothe and comfort patients, particularly those suffering from "shell-shock."

Sources consulted: Gordon Daniels, Sister Ethel McCaul R.R.C. (1867-1931) And The Japanese Red Cross (2010); "Ethel Rosalie Ferrier McCaul," Lives of the First World War; "McCaul Hospital for Officers," Lost Hospitals of London; The Union Jack Club, "Our History"