Gwynedd (English: ; Welsh: [ˈɡʊɨnɛð]) is a county and preserved county (latter with differing boundaries; includes the Isle of Anglesey) in the north-west of Wales. It shares borders with Powys, Conwy County Borough, Denbighshire, Anglesey over the Menai Strait, and Ceredigion over the River Dyfi. The scenic Llŷn Peninsula and most of Snowdonia National Park are in Gwynedd. Bangor is the home of Bangor University.

As a local government area, it is the second largest in Wales in terms of land area and also one of the most sparsely populated. A majority of the population is Welsh-speaking. Gwynedd also refers to one of the preserved counties of Wales, covering the two local government areas of Gwynedd and Anglesey. Named after the old Kingdom of Gwynedd, both culturally and historically, Gwynedd can also be used for most of North Wales, such as the area that was policed by the Gwynedd Constabulary. The current area is 2,535 square kilometres (979 square miles), almost exactly the size of Luxembourg, with a population of 121,874 as measured in the 2011 census. The population decreased significantly at the 2021 census to 117,393.