Kumarsain Assembly constituency was one of the 68 constituencies until 2008 delimitation in the Himachal Pradesh Legislative Assembly of Himachal Pradesh state in India. It was a segment of Simla Lok Sabha constituency. It included areas of Kumarsain tehsil and Sunni tehsil of Shimla district. Post 2008 delimitation, Kumarsain tehsil became part of Theog Assembly constituency and Sunni tehsil became part of Shimla Rural Assembly constituency.