51°02′47″N 01°18′38″W / 51.04639°N 1.31056°W
| Site of Special Scientific Interest | |
 | |
| Location | Hampshire |
|---|---|
| Grid reference | SU 485 274[1] |
| Interest | Biological, historic |
| Area | 43 hectares (110 acres)[1] |
| Notification | 1986[1] |
| Location map | Magic Map |
St. Catherine's Hill is a chalk downland hill and 43-hectare (110-acre) biological Site of Special Scientific Interest on the outskirts of Winchester in Hampshire, England. It is owned by Winchester College but open to the public. It is managed by Hampshire and Isle of Wight Wildlife Trust, and topped by an Iron Age hillfort, a scheduled monument. In the Black Death, plague pits were dug in the dry valley on the south side of the hill. In the Early modern period, a mizmaze was cut on the hilltop. Winchester College football used to be played on the hill; in an old custom, members of the college assemble on the hill every year, early in the morning.
Geologically, the hill is part of a local anticline in the chalk, which is of Turonian age in the Upper Cretaceous. The local ecology is dominated by the chalk, which results in a thin dark soil, a rendzina, which favours lime-loving plants from orchids to bellflowers.