Pilsey Island is a 17.8-hectare (44-acre) Local Nature Reserve in Chichester Harbour in West Sussex.

It is owned by the Ministry of Defence[1][2] and managed by the Royal Society for the Protection of Birds.

[3] It is part of the Chichester Harbour Site of Special Scientific Interest[4] and Nature Conservation Review site, Grade I*,[5] the Chichester and Langstone Harbours Ramsar site[6] and Special Protection Area, [7] and the Solent Maritime Special Area of Conservation.

[8] The island has sand dunes, mudflats, salt marsh and bare and vegetated shingle.

There are many plants, spiders and insects.