This thesis asks what the demographics of elite marathon runners are and how they have changed over the past 40 years. Differences in age and nationality of elite marathon runners are examined for the top 100 men’s and women's marathon results each year from 1983 to 2022. This thesis found that 28 is the best age for an elite marathoner to run their best time and that the nations producing top marathon runners are more concentrated now than in the 1980s, prompting the question of whether the resources provided to athletes showing potential are more focused in a select few countries.