 Killywillin is bounded on the north by Gortaclogher and Killymoriarty townlands, on the west by Killyran townland, on the south by Ballymagauran and Derryragh townlands and on the east by Porturlan townland.Its chief geographical features are Killywillin Lough, the River Blackwater, County Cavan, spring wells and a quarry.Killywillin is traversed by the regional R205 road (Ireland), minor roads, rural lanes and the disused Cavan and Leitrim Railway.