Coombe Hill Hollow is a 4.3 hectare biological Site of Special Scientific Interest north of Sibbertoft in Northamptonshire. This steep narrow valley has neutral grassland which has never been subject to fertilisers or herbicides, and it has diverse flora. Grasses include brown bent, red fescue, Yorkshire fog and crested dog's-tail. Lime-rich areas have harebell and mouse-ear hawkweed, and there are locally important butterfly populations. Other habitats include bramble, gorse and woods. The site is private land with no public access.