Dead Diamond River
The Dead Diamond River at Gate Camp, Second College Grant, NH
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Location
Country	United States
State	New Hampshire
County	Coos
Townships	Atkinson and Gilmanton Academy Grant, Second College Grant
Physical characteristics
Source	Confluence of West and East branches
• location	Atkinson and Gilmanton Academy Grant
• coordinates	45°0′9″N 71°8′54″W / 45.00250°N 71.14833°W / 45.00250; -71.14833
• elevation	1,435 ft (437 m)
Mouth	Magalloway River
• location	Second College Grant
• coordinates	44°52′32″N 71°3′0″W / 44.87556°N 71.05000°W / 44.87556; -71.05000
• elevation	1,246 ft (380 m)
Length	18.7 mi (30.1 km)
Basin features
Tributaries
• left	Horne Brook, Washburn Brook, Merrill Brook
• right	Tracy Brook, Little Dead Diamond River, Lamb Valley Brook, Loomis Valley Brook, Swift Diamond River

The Dead Diamond River is an 18.7-mile-long (30.1 km)^[1] river in northern New Hampshire in the United States. Its water enters the Atlantic Ocean on the coast of Maine by passing through the Magalloway, Androscoggin, and Kennebec rivers.

The Dead Diamond River is formed in the township of Atkinson and Gilmanton Academy Grant, New Hampshire by the juncture of the West Branch and the East Branch. The Dead Diamond heads south through logging country, and the Little Dead Diamond River joins from the west at Hell Gate, a set of rapids, just before the Dead Diamond enters the Dartmouth College Grant. The river traverses the length of the college grant before reaching the Magalloway River near the Maine border. The Swift Diamond River is a significant tributary which joins the Dead Diamond shortly upstream of the Magalloway.

• List of rivers of New Hampshire