The Forrestdale and Thomsons Lakes Ramsar Site comprises two separate nature reserves, totalling in area, protecting two shallow fresh to brackish, seasonal lakes in a suburban and agricultural landscape in south-western Western Australia. It lies in the Swan Coastal Plain bioregion and is used mainly for birdwatching and walking. The site is recognised as being of international importance under the Ramsar Convention on Wetlands, under which it was designated Ramsar Site 481 on .