The Grattai Mountain, a mountain located within the Nandewar Range, is situated within the North West Slopes region of New South Wales, Australia. The mountain was formed by the Nandewar Volcano around 21 million years ago. The mountain has an elevation of 1,301 metres above sea level and lies within the Mount Kaputar National Park. It is rarely climbed due to its isolation, lack of walking tracks and the cliffs which almost encircle the summit plateau.