Slemmestad is a village in Røyken municipality, Norway. Slemmestad is located on the Oslofjord, west of Oslo, Norway.
Historically Slemmestad was located on the old highway running between from Oslo and Drammen. Until the establishment of cement factory in 1888, this was a pure farming village. The largest farms were the Lillelien, together with øvre and nedre Slemmestad. Slemmestad was built around the Aktieselskabet Christiania Portland Cementfabrik cement plant. Aktieselskabet Christiania Portland Cementfabrik, later Slemmestad sementfabrikk, was in operation from 1893 to 1989. The company was for many years the principal manufacturer of cement within Norway. The factory was rebuilt several times with new and more modern cement kilns. Cement production peaked in 1973 when it produced 1,082,677 tons.
Slemmestad forms part of the Oslo Geological Region (Oslofeltet). This is an ancient, sunken part of the crust reaching in the south at sea level and extending north to Brumunddal in the Ringsaker municipality of Hedmark County. By subsidence, the Oslo field had preserved a comprehensive sequence of shale, limestone, siltstone and sandstone of the Cambrian period.
Slemmestad Cement Museum (Slemmestad Cementmuseum) is located in the cement factory's former bag factory in Slemmestad. The museum was opened in 1991. It features photographs, artifacts, records and other documentation that shows 100 years of development of cement production and the great importance of the factory was Slemmestad and the people who lived there.
Slemmestad church is a wooden structure and has 200 seats. It was dedicated on 25 August 1935. The architect for the church was Ivar Næss. The building was expanded eastward in 1960 with vestry and secondary rooms, and this extension was extended eastwards in 1978. Slemmestad chapel and cemetery are in the southern part of the village, around half kilometer from Slemmestad church. The cemetery was inaugurated in autumn 1923.