Gwent Wildlife Trust (Welsh: Ymddiriedolaeth Natur Gwent) (GWT) is a wildlife trust covering the area between the lower Wye and Rhymney rivers which forms the vice county of Monmouthshire in south-east Wales. It is a registered charity and a member of the Wildlife Trusts Partnership.
Its origins lie in the Monmouthshire Naturalists Trust, formed in 1963. In the 1980s the Trust was renamed the Gwent Trust for Nature Conservation, and then Gwent Wildlife Trust. Gwent was an administrative county between 1974 and 1996, covering a similar but not identical area to the historic county of Monmouthshire.
The Trust's first objective, under the then presidency of FitzRoy Somerset, 4th Baron Raglan, was the conservation of Magor Marsh, the last remaining area of fenland on the Caldicot Level. It was particularly responsible for survey work, training programmes, and increasingly in educational projects and in campaigns against inappropriate development proposals, particularly those affecting the Severn estuary. In 1991 it purchased Pentwyn Farm at Penallt, a unique smallholding, including ancient meadows and a collapsing medieval barn, having raised the purchase price of £150,000 within six weeks through a public appeal. In 2001 it bought Springdale Farm near Usk, containing 40 acres (16 ha) of species-rich unimproved grassland, 60 acres (24 ha) of other grassland, and an ancient wood. It now manages 32 reserves, and has a membership of some 7,500.