| State: | SD |
| Type: | SD |
| Route: | 71 |
| Alternate Name: | Cascade Road |
| Map Custom: | yes |
| Map Notes: | SD highlighted in red |
| Length Mi: | 34.535 |
| Length Ref: | [1] |
| Established: | 1962 |
| Direction A: | South |
| Terminus A: | northwest of Crawford, NE |
| Direction B: | North |
| Terminus B: | in Hot Springs |
| Counties: | Fall River |
| Previous Type: | SD |
| Previous Route: | 65 |
| Next Type: | SD |
| Next Route: | 73 |
| Section: | 175 |
South Dakota Highway 71 (SD 71) is a 34.535miles state highway in Fall River County, South Dakota, United States, that travels from the Nebraska state line (where it continues as N-2/N-71 through the Black Hills National Forest) to U.S. Route 18 Bypass (US 18 Byp.) in Hot Springs. It is part of a triple state highway serving South Dakota, Nebraska, and Colorado.
SD 71's southern terminus is at the Nebraska border in Black Hills National Forest where it has the same number.
In the forest, the route meets the terminus of South Dakota Highway 471. After that, it leaves the forest and ends at US 18 Byp. in Hot Springs.
The road was originally commissioned in 1936 as part of South Dakota Highway 87. Part of that highway was given the SD 71 designation in 1962.