The Zymoetz River (formerly Copper River) is a tributary of the Skeena River in northwestern part of the province of British Columbia, Canada. From its source in the Bulkley Ranges of the Hazelton Mountains the Zymoetz River flows southeast for about 145 km (90 mi) to empty into the Skeena River in the Zaimoetz 5 Indian Reserve of the Kitselas First Nation.

The Zymoetz River's drainage basin covers 3,026 km² (1,168 sq mi). The river's mean annual discharge is estimated at 114 m³/s (4,000 cu ft/s), with most of the flow occurring between May and October. According to the stream gauge "08EF005 Zymoetz River Above O.K. Creek", the Zymoetz's maximum recorded instantaneous discharge was 3,140 m³/s (111,000 cu ft/s), on 1 November 1978. The Zymoetz watershed's land cover is classified as 56.8% conifer forest, 17.8% barren, 13.3% snow/glacier, and small amounts of other cover. The mouth of the Zymoetz River is located about 8 km (5.0 mi) west of Terrace, British Columbia, about 57 km (35 mi) north of Kitimat, about 120 km (75 mi) east of Prince Rupert, British Columbia, and about 380 km (240 mi) west of Prince George, British Columbia.

Most of the Zymoetz River's drainage basin lies within the traditional territory of the Tsimshian Kitselas First Nation of the Kitselas people. The Burnie River tributary area is part of the traditional territory of the Wetʼsuwetʼen First Nation.

The meaning of "Zymoetz" is unclear. It may come from a Tsimshianic word meaning "palm of the hand".

The Zymoetz River originates in the Bulkley Ranges, a subrange of the Hazelton Mountains, on the west side of Hudson Bay Mountain, west of the town of Smithers. The upper Zymoetz River flows westward through Aldrich Lake, Dennis Lake, and McDonell Lake. It is joined by tributary streams including Silvern Creek, and Passby Creek. After exiting McDonell Lake the Zymoetz continues flowing west, collecting the tributaries of Serb Creek, Sandstone Creek, Coal Creek, Mulwain Creek, and Red Canyon Creek, then turns south. The middle, southward flowing portion of the Zymoetz River collects tributaries including Treasure Creek, Blackberry Creek, Miligit Creek, Many Bear Creek, Nogold Creek, Mattock Creek, and Limonite Creek, South of the Limonite confluence the Zymoetz River is joined by the Kitnayakwa River, after which the Zymoetz turns to flow west.

In its lower westward flowing reach, the Zymoetz runs between the Bornite Range and the O.K. Range, both part of the Hazelton Mountains. It is joined from the south by its largest tributary, the Clore River, then Salmon Run Creek, which joins from the north. After that the Zymoetz is joined by Mattson Creek, McNeil Creek, Dardanelle Creek, O.K. Creek, Eight Mile Creek, and Magee Creek. A few kilometers after Magee Creek, the Zymoetz River empties into the Skeena River within Zaimoetz Indian Reserve No. 5 of the Kitselas First Nation.

Most of the Zymoetz River's tributaries are small. The largest is the Clore River, which drains 985 km² (380 sq mi) south of the Zymoetz River, and has an average discharge of 44.2 m³/s (1,560 cu ft/s). The Clore River's main tributary is the Burnie River, with a drainage basin 364 km² (141 sq mi) large and an average discharge of 11.9 m³/s (420 cu ft/s). Other notable tributaries of the Zymoetz River include the Kitnayakwa River, which drains an area 260 km² (100 sq mi) large, and has an average dischage of 12.3 m³/s (430 cu ft/s) average discharge; Serb Creek, with a 160 km² (62 sq mi) large basin size, and an average discharge of 5.73 m³/s (202 cu ft/s); and Mulwain Creek, with a 132 km² (51 sq mi) large basin size, and an average discharge of 3.81 m³/s (135 cu ft/s).

Near its confluence with the Skeena River the Zymoetz River is crossed by British Columbia Highway 16, which runs along the Skeena River. Canadian National Railway tracks run along the north side of the Skeena River.