Sybil Rachel Betty Cecile Cholmondeley, Marchioness of Cholmondeley CBE (/ˈtʃʌmli/ CHUM-lee, born Sybil Rachel Betty Cecile Sassoon; 30 January 1894 – 26 December 1989), styled Countess of Rocksavage from 1913 to 1923, was a British socialite, patron of the arts, and Chief Staff Officer in the Women's Royal Naval Service (WRNS) during the Second World War.

She was the daughter of Sir Edward Sassoon (1856–1912), 2nd Bt., and Baroness Aline Caroline de Rothschild (1865–1909).

They had two sons and one daughter: Lady Cholmondeley was largely responsible for restoring her husband's family estate, Houghton Hall, to its former glory.

[2] In "the pool garden", the entwined initials "SS" are represented in the outlines of the clipped box-hedge which surrounds plantings of lavender and rosemary.

On 9 February 1945 she was appointed as Superintendent of the Women's Royal Naval Service (WRNS) and the following year was made CBE.