Northumberland County (2001 population 50,817), the largest in the Province, is located in northeastern New Brunswick, Canada. The county is dominated by the Miramichi River, world famous for its salmon fishing. Northumberland County is covered by thick forests, whose products stimulate the economy. Its eastern portion is washed by Miramichi Bay, a part of the Gulf of St. Lawrence.

The County is a mostly English speaking region in the otherwise Francophone east New Brunswick. The lower regions along Miramichi Bay are French speaking. The former town of Chatham, New Brunswick has traditionally been an Irish stronghold, while its sister town of Newcastle, New Brunswick has had a more English and Scottish Protestant flavour. Both are now part of the new city of Miramichi. There are three native Mi'kmaq communities located at Red Bank, at the junction of the Northwest Miramichi and the Little Southwest Miramichi Rivers, at Eel Ground, close to the junction of the Northwest and Southwest Miramichi Rivers and at Burnt Church on the north coast of Miramichi Bay.

There is a large pulp mill just upriver from Miramichi, close to the junction of the Northwest and Southwest Miramichi rivers. It has been in operation with various upgrades since before World War Two. Ownership has frequently changed. There are smaller forest manufacturing establishments at a number of locations. A Federal Maximum security prison at Renous provides steady employment. Less certain are the offices of the national gun registry, now located in the former town of Chatham, New Brunswick.

List of towns in Northumberland County, with 2001 populations given:

• Miramichi (18,508)
• Neguac (1,697)
• Baie-Sainte-Anne (1,600)
• Rogersville (1,248)
• Brantville (1,153)
• Blackville (1,015)
• Doaktown (955)
• Sunny Corner (910)
• Tabusintac (893)
• Renous (885)
• Riviere-du-Portage (725)
• St. Margarets (386)
• Black River Bridge (371)
• Escuminac (252)
• Boiestown (???)