Agnes Keyser, DStJ, RRC (11 July 1852 – 11 May 1941) was a British humanitarian and longtime mistress to Edward VII, King of the United Kingdom.

[2][3] Her ancestors were Jewish and arrived in Britain from Central Europe in the eighteenth century, and her ancestral country house was Cross Oak, Berkhamsted, Hertfordshire.

[2] The two sisters enjoyed the social scene in London, and their father subsequently bought them 17 Grosvenor Crescent, Hyde Park Corner, where they entertained guests and built up a friendship circle of "the best people".

To support efforts in the war, many people came together to contribute, and on this background the Keyser sisters agreed to offer their Belgravia mansion to care for wounded officers, at the suggestion of the Prince of Wales.

[2] At the suggestion of the Prince, Keyser became Sister Agnes, and the house at Grosvenor Crescent, with its initial 12 beds, greeted the first wounded officers in February 1900.