Cllr Benn, who represents Glen ward, has resigned on health grounds.
He has represented the residents in his ward, which covers the parishes of Careby, Aunby and Holywell, Castle Bytham, Carlby, Counthorpe and Creeton, Little Bytham and Toft with Lound and Manthorpe, since last year's local elections on May 2.
Cllr Benn is also Chairman of the Council's Environment Overview and Scrutiny Committee. The Council will appoint a new Chairman for the Environment OSC on 16 July 2020.
Cllr Benn is a much valued and popular member of South Kesteven District Council and he will be missed by members and staff alike. Due to Covid-19, the earliest date for a by-election at present is 6 May, 2021, coinciding with the County Council and Police and Crime Commissioner elections.
Leader of South Kesteven District Council, Cllr Kelham Cooke, said: "Chris has only been with South Kesteven District Council for a short time, but his contribution during that period as a ward member, member of the Conservative Group, and Chairman of the Environment Overview and Scrutiny Committee has been significant, and he will be sorely missed.
"I am sure I speak for the whole council in wishing him and his family well, and looking forward to his continued contributions to our community as a resident, and a friend of the council."