Top o'Selside is a hill in the Lake District in Cumbria, England. At 335 m, it is the highest point of the group of hills situated between Coniston Water and Windermere. This group also includes the Wainwright of Black Fell and the summits of Black Brows and Rusland Heights. Top o'Selside lies not in the centre of this region, but in the south-western corner, just outside the forestry plantations of Grizedale Forest and only two-thirds of a mile from the eastern shore of Coniston Water. This large separation from any higher ground gives it enough relative height to make it a Marilyn.
It is also listed in A. Wainwright's Pictorial Guide to the Outlying Fells, where the author gives a walk from High Nibthwaite over the subsidiary summits of High and Low Light Haw. This walk is a little over four miles and involves about a thousand feet of climb. Wainwright's location is not the highest point of the fell, being 100m to the west of the true summit and 1m lower.