Nathaniel "Nat" Muir (born 12 March 1958) from Salsburgh North Lanarkshire is a Scottish retired long-distance runner. He competed at the IAAF World Cross Country Championships on ten occasions, four times as a junior from 1974 to 1977 and six times as a senior between 1978 and 1987. Muir took up athletics in 1970 while at primary school in Chapelhall. He was encouraged by his fellow pupils to join the Shettleston Harriers running club, and his first race was the Lanarkshire Relays in 1970, which saw him earn the fastest individual time in his age group.