The Sensorites is the seventh serial in the British science fiction television series Doctor Who. Written by Peter R. Newman and directed by Mervyn Pinfield and Frank Cox, the serial was first broadcast on BBC1 in six weekly parts from 20 June to 1 August 1964. In the serial, the First Doctor, his granddaughter Susan Foreman, and her teachers Ian Chesterton and Barbara Wright visit a planet known as the Sense-Sphere to find the cure to a disease afflicting the alien race the Sensorites.

Ian Chesterton is a fictional character in the British science fiction television series Doctor Who and a companion of the First Doctor. He was played in the series by William Russell and was one of the members of the programme's first regular cast, appearing in much of the first two seasons from 1963 to 1965. In a film adaptation of one of the serials, Dr. Who and the Daleks (1965), he was played by Roy Castle, but with a very different personality and backstory. Ian appeared in 16 stories and 77 episodes. He later returned for a cameo appearance, played once again by Russell, in the 2022 episode "The Power of the Doctor".