Paper and pulp industry in Dryden, Ontario

The Dryden pulp mill, also known as the Reed Mill, is a paper and pulp mill in Dryden, Ontario. During the 1960s and 70s, mercury poisoning from the mill caused one of Canada's worst environmental disasters: Dryden Chemicals Ltd dumped mercury into the English-Wabigoon River, upstream of Grassy Narrows First Nation, poisoning the fish which were their staple food. Members of the Grassy Narrows and the Whitedog communities downstream from the mill suffered severe mercury poisoning. Additionally, the mill was the subject of a W5 investigative report, published in 2021, into claims that workers involved in the Recovery Boiler #4 (RB4) project were intentionally exposed to toxic fumes by their employer during its construction between 2002 and 2004. As of 2024, the RB4 project is also the subject of an ongoing occupational disease investigation by Occupational Health Clinics for Ontario Workers (OHCOW).

The first iteration of the mill was initially built by Charles and Grant Gordon in 1909 on the west side of the Wabigoon River From the early twentieth century to the twenty-first century, the forest industry has played a significant role in Dryden's economy.

In 2019, the Supreme Court of Canada ruled that Weyerhaeuser Company and Resolute Forest Products—previously known as Abitibi-Consolidated—are responsible for remediating the mercury contamination. The environmental poisoning continues to cause significant health problems for the First Nations communities downstream. The Government of Canada is building a $20 million clinic to treat the First Nations "suffering from mercury poisoning".

Since a US$520 million purchase of the mill by Domtar from Weyerhaeuser, in 2007 the mill has produced Northern Bleached Softwood Kraft pulp product.