Ian Chesterton is a fictional character from the British science fiction television series Doctor Who. He first appeared in the show's inaugural episode in 1963 and was portrayed by actor William Russell. Ian is a science teacher and one of the original companions of the First Doctor, traveling through time and space in the TARDIS. Throughout his adventures, Ian is known for his bravery and resourcefulness. He often takes on a protective role, especially towards his fellow companion, Barbara Wright, who is also a teacher. Ian's character contributed significantly to the early dynamics of the show, helping to establish the format of the Doctor's companions.