Gatundu South is an electoral constituency in Kiambu County, Kenya and the seat of the District Officer in Gatundu Town. It is one of twelve constituencies in Kiambu County which comprises four wards: Kiamwangi, Kiganjo, Ndarugo, and Ng'enda. All of them are within the Kiambu County Council. The constituency was established before the 1997 General Elections. Previously it was part of the larger Gatundu Constituency which was split into Gatundu South Constituency and Gatundu North Constituency. It is ranked 182 out of 210 Constituencies in Kenya in size and 165 out of 210 in population size.
The current Member of Parliament is Gabriel Kagombe who succeeded Moses Kuria in 2022.