Katherine Emily Eggar (5 January 1874 – 15 August 1961) was an English pianist and composer. Eggar was born and died in London, England, the daughter of Thomas Eggar and Katherine MacDonald. Eggar was active member of the feminist movement especially in terms of opportunities for women in music. At the inaugural meeting of the Society of Women Musicians, Eggar stated, "The conventions of music must be challenged. Women are already challenging conventions in all kinds of ways… We believe in a great future for women composers." (Katherine Emily Eggar, at the inaugural meeting in 1911 of the Society of Women Musicians which she helped found)