Stora Enso Oyj (from Swedish: Stora [ˈstǔːra] and Finnish: Enso [ˈenso]) is a Finnish and Swedish forest industry company. It develops and produces various materials, mostly based on wood, for a range of industries and applications worldwide. It has headquarters in Helsinki, Finland, and Stockholm, Sweden. The majority of sales takes place in Europe, but there are also significant operations in Asia and South America. Stora Enso was formed in 1998, when the Swedish mining and forestry products company Stora AB merged with the Finnish forestry products company Enso Oyj. In 2023, there were 20,000 employees. In 2015, Stora Enso was ranked seventh in the world by sales and fourth by earnings, among forest, paper and packaging industry companies. For the first two quarters of 2018, the company was ranked second by net earnings among European forest and paper industry companies. The corporate history can be traced back to the oldest known preserved share certificate in the world, issued in 1288 by Stora Kopparberg. Based on this, some observers consider Stora Enso to be the oldest limited liability company in the world.

Stora Enso was formed by the merger of Swedish mining and forestry products company Stora and Finnish forestry products company Enso Oyj in 1998.

The oldest preserved share in the Swedish copper mining company Stora Kopparberg (Falun Mine) in Falun was issued in 1288. It granted the Bishop of Västerås 1/8th (12.5%) ownership, and it is also the oldest known preserved share in any company in the world. The corporate status of the company was further recognized in 1347, when King Magnus IV of Sweden granted it a charter. Some observers consider that these facts make Stora and its successor Stora Enso the oldest existing corporation or limited liability company in the world.

For some periods during the 17th century, the mine provided two thirds of the world production of copper. In the 18th century, the copper mining gradually decreased in importance, and therefore, in 1731, the company bought its first iron ore mine. By the 1860s, iron ore was economically more important to the company than copper.

Stora Kopparbergs Bergslags AB was incorporated as a modern shareholder company in 1862. Towards the end of the 19th century, it diversified from mining and entered pulp and paper production. In the 1970s, most of the mining and steel mill operations of the company were divested, and the focus changed to forestry-related activities. In 1984, the company name was shortened to Stora AB. The copper mine closed down in 1992.

In 1997, the year before the merger with Enso, Stora had 20,400 employees and a turnover of 44.5 billion SEK. The company owned 2.3 million hectares of forest of which 1.6 million hectares (an area larger than Connecticut) in Sweden and the rest in Canada, Portugal and Brazil. It also produced 7.5 TWh of mostly hydroelectric power.

A 1997 article in Harvard Business Review praised Stora's ability to adapt to changing circumstances over the centuries.

In 1998, the company merged with Enso to form Stora Enso.