|Blacks Fork of the Green River|
|Cities||Green River, Wyoming, Lyman, Wyoming, Granger, Wyoming|
|- location||Uinta Mountains, Utah|
|Mouth||Flaming Gorge Reservoir|
Blacks Fork (also referred to as Blacks Fork of the Green River) is a 175-mile-long (282 km) tributary of the Green River in Utah and Wyoming. The river rises on the northern side of the Uinta Mountains as the combination of three streams draining the area around Tokewanna Peak near the Utah-Wyoming border. Right as the river crosses the Wyoming border, it flows into Meeks Cabin Reservoir which is used for irrigation and flood control. From there the river flows through the town of Lyman before joining with the Smiths Fork, which forms just east of the Blacks Fork in the Unitas, and parallels it for most of its course. The river continues northeast to Granger, where the river meets the Hams Fork from the north. Shortly thereafter the river makes a sharp turn south, eventually joining the Green River at Flaming Gorge Reservoir.
In 1843 mountain man Jim Bridger and his partner Louis Vasquez constructed a trading post on the Blacks Fork, located near present day Lyman, known later as Fort Bridger. The post soon became a popular stop along the Oregon and California trails and later marked the point at which the Mormon Trail left the other two and continued into Utah.