Sir Lionel Ernest Howard Whitby, CVO, MC (8 May 1895 – 24 November 1956) was a British haematologist, British Army officer and academic. He served as Regius Professor of Physic at the University of Cambridge from 1945 to 1956, Master of Downing College, Cambridge from 1947 to 1957, and Vice-Chancellor of the University of Cambridge from 1951 to 1953.
Whitby was born on 8 May 1895 in Yeovil, Somerset. He was the second of three sons born to Benjamin Whitby and his wife, Jane Elizabeth Whitby (née Milborne). He was educated at King's College, an independent school in Taunton, Somerset, and at Bromsgrove School, an independent school in Bromsgrove, Worcestershire. In 1914, having completed his schooling, he was awarded a senior open scholarship to attend Downing College, Cambridge. However, he did not immediately take up his place at the University of Cambridge, and instead enlisted in the military at the start of World War I.
Having returned from military service as a decorated but disabled officer, he returned to studies. In October 1918, he took up his scholarship and matriculated into Downing College, Cambridge, to study medicine. After completing his theoretical studies he moved to Middlesex Hospital in London to complete his training. He was awarded the Freeman Scholarship and the Leopold Hudson Prize in 1922, and the Hetley Clinical Prize in 1923. In 1923, he graduated Bachelor of Medicine, Bachelor of Surgery (MB BCh). He was awarded a Diploma of Public Health (DPH) in 1924.