Hart Side is a Lake District fell of 756 m in Westmorland and Furness. It rises only 24 m above its key col, 3.2% of its height.
Its key col leads to Helvellyn, not to its nearest higher summit, Green Side. Its nearest higher summit, Green Side (794.1 m, 1.2 km south-west), is a listed top not profiled here. The key col is close by, only 0.4 km to the south-west at 732 m.