Thunder Bay–Atikokan is a provincial electoral district in northwestern Ontario, represented in the Legislative Assembly of Ontario since 1999.

The riding was created in 1999 from portions of Port Arthur, Fort William, Lake Nipigon, and Rainy River when Ontario aligned its provincial boundaries with federal electoral districts.

In 2005, new legislation confirmed that Ontario would be divided into 107 provincial ridings beginning with the 2007 election. As part of this, Thunder Bay–Atikokan was maintained as one of 11 northern Ontario ridings, ensuring fair representation for the region.

The district includes both urban and rural communities, combining the city of Thunder Bay’s western portion with towns and smaller communities such as Atikokan. Known for its natural resources, mining, and tourism industries, Thunder Bay–Atikokan reflects the unique mix of urban life and northern Ontario culture.