Thy (Danish pronunciation: [ˈtʰyˀ], local dialect [ˈtʰyi̯kʲʰ]) is a traditional district in northwestern Jutland, Denmark. It is situated north of the Limfjord, facing the North Sea and Skagerrak, and has a population of around 44,000. The capital is Thisted. Snedsted, Hanstholm and Hurup are minor towns in the area.

Since the Danish municipal reform of 1 January 2007, Thy is roughly identical with Thisted Municipality which belongs to the North Denmark Region. The southernmost part of Thy, the Thyholm Peninsula, belongs to Struer Municipality in the Central Denmark Region. Before the merger, Thy consisted of four municipalities: Hanstholm, Thisted, Sydthy and Thyholm.

Thy forms the western part of the North Jutlandic Island and borders Hanherred to the northeast with Vendsyssel even further northeast. In the Limfjord is the island of Mors, considered a twin district of Thy, and south of the fjord is Hardsyssel in western mainland Jutland. Thy is traditionally regarded part of northern and western Jutland alike. The dialect belongs to the West Jutlandic group.

Thy has a very varied landscape. In the north it is marked by flat coastal plains which were covered by sea in Neolithic times, but fell dry because of the post-glacial rebound. These are interrupted with higher-lying plains that were islands in the Neolithic sea. In the slopes that formed the coast in these times, high-lying limestone is often visible - hence the name of the Limfjord. The eastern stretch, facing the Limfjord, has quite fertile soil, is slightly hilly and dotted with small villages and farms like the landscape in most of rural Denmark. The landscape is marked by strong western winds, most trees bending eastwards.

The west coast has wide beaches and high dunes with Leymus grass and sea-buckthorn. Behind the dunes, there is heath with stretches of Calluna heather, Iceland moss, Cladonia, crowberry, bilberry, blueberry, cranberry and orchids including the unique Dactylorhiza majalis subsp. calcifugiens. This is the result of huge sand drifts in the 15th to 19th centuries which covered much formerly fertile land. The sand drifting affected the whole west coast of Jutland, and various other parts of Denmark as well like Tisvilde on Zealand for example. Since Thy is exposed to winds from both the north and the west, even from the North Atlantic, the sand drift went the furthest inland in this area, as far as 18 km (11 mi). Parts of the sandy stretches have been turned into conifer woods. A line of lakes, believed to have been caused by the sand drifts blocking the outflow to the sea, mark the border between the western, sparsely populated sandy area and the eastern, fertile farmland.

The wetlands Vejlerne in the northeast are the largest bird sanctuary in Northern Europe. Nearby is the bird cliff Bulbjerg.

On 22 August 2008, Thy National Park officially opened, as the first of three realized national parks out of seven planned.

On 10 July 2007, a police officer from Hanstholm found a hermit in the state forest of Hjardemål Klit, one of the more deserted areas in the north of Thy. For three years, the middle-aged man from Zealand had been living in the primitive forest shelters of the district and made a living from collecting empty bottles. For the same period he had been missed by his parents, who thought he was dead, but he was now re-united with them on the initiative of the police officer. Forest workers told they were aware of the man's existence, particularly that he had left behind many eggshells at the shelters and seemingly was nourished on eggs, but since he didn't do any harm they had left him alone.