Beddmanarch–Cymyran is a site of special scientific interest (SSSI) on the Welsh island of Anglesey extending to just over 900 hectares (2,200 acres), and centred on the Cymyran Strait.

All of these support a variety of wildlife including breeding birds, such as arctic and common terns, and plants like dwarf rush (Juncus capitatus) and spiral tasselweed (Ruppia cirrhosa).

[3] As a marine protected area the site is important for the common ringed plover (Charadrius hiaticula), common greenshank (Tringa nebularia), eel grass and tide-swept algae, and for its inter-tidal, salt marsh, muddy gravel, and sheltered mud environments.

[5] While many activities can damage protected sites, Beddmanarch–Cymyran SSSI is sensitive to a number of possible changes and activities:[3] A wide variety of operations may affect the site and require consultation with Natural Resources Wales and may further require consent.

28 operations are currently listed and include activities relating to farming, fishing, water utilisation, and the introduction or removal of flora and fauna.