Marine nature reserve (MNR) is a conservation designation officially awarded by a government to a marine reserve of national significance.
Marine nature reserves were introduced in the UK by the Wildlife and Countryside Act 1981, and were designed to conserve marine life and geological or physiographical features of special interest.
They have similar status and protection to national nature reserves, but were specifically concerned with a marine environment, including both the sea and seabed.
In the UK, there are only three statutory MNRs: Lundy Marine Nature Reserve at Lundy Island (Bristol Channel), Skomer Marine Nature Reserve (Pembrokeshire) and Strangford Lough (County Down).
There is a non-statutory voluntary MNR at St Abbs Head, Berwickshire.