Kathleen Bever Blackburn, FLS (1892–1968) was a British botanist best remembered for the 1923 discovery that plant cells have sex chromosomes.

Her father, E. P. Blackburn, was a prominent minister in the Methodist Church, ending his career at Jesmond after a number of ministries around the United Kingdom.

Her first published work, in 1917, was an anatomical study of vascular tissue in seedlings of the buttercup family, Ranunculaceae and others.

[2]: 51 She then studied the campions (genus Silene) and established that female and male flowers of these plants had X and Y sex chromosomes (Blackburn 1923, 1924).

The fact that X and Y sex chromosomes are actually quite rare in plants, occurring only in a minority of dioecious species (in which the male and female flowers are borne on separate individuals), was known to her.

In the 1940s she became involved in researching soils and peat bogs in connection with the development of the Kielder Forest by the Forestry Commission.

Her skills at reconstructing past vegetation using both pollen analysis and examination of larger plant fragments were utilised by archaeologists working on Hadrian's Wall and elsewhere in the North East of England.

[9] She appears never to have married, and seems to have lived in the family home in Jesmond, Newcastle upon Tyne, at least in later years, with her sister, Dorothy.