Koidu is a city in Sierra Leone.
Koidu may also refer to one of several villages in Estonia: Koidu, Harju County, village in Saue Parish, Harju County Koidu, Lääne County, village in Haapsalu, Lääne County Koidu, Viljandi County, village in Viljandi Parish, Viljandi County
See also Koidu, Saare County, former village in Lääne-Saare Parish, Saare County, now part of Suur-Randvere village Koidu-Ellavere, village in Koeru Parish, Järva County, Estonia