Rosalind Cecilia Hildegard Tanner (née Young) (5 February 1900 – 24 November 1992) was a mathematician and historian of mathematics. She was the eldest daughter of the mathematicians Grace and William Young. She was born and lived in Göttingen in Germany (where her parents worked at the university) until 1908. During her life she used the name Cecily. She then studied at Girton College, Cambridge, gaining a PhD in 1929 under the supervision of Professor E. W. Hobson for research on Stieltjes integration. She accepted a teaching post at Imperial College, London where she worked until 1967.