Thatcham Reed Beds is a 66.9 hectare (165.3 acre) Site of Special Scientific Interest in the civil parish of Thatcham in the English county of Berkshire, notified in 1974. It is also a Local Nature Reserve. The site is managed by the Berkshire, Buckinghamshire and Oxfordshire Wildlife Trust.
Located at grid reference SU507665, Thatcham Reed Beds is important nationally for its extensive reed bed, species rich alder woodland and fen habitats. The latter supports Desmoulin's whorl snail (Vertigo moulinsiana), which is of national and European importance. A large assemblage of breeding birds including nationally rare species such as Cetti's warbler (Cettia cetti) is also associated with the reedbed, fen and open water habitats found at Thatcham Reed Beds.
Thatcham's network of gravel pits, reedbed, woodland, hedges and grassland is rich in wildlife and has been made into The Nature Discovery Centre by the Royal Society for the Protection of Birds.