| Arroyo Las Positas | |
| stream | |
| Name origin: Spanish | |
| Country | United States |
|---|---|
| State | California |
| Region | Alameda County |
| Cities | Livermore, Dublin |
| Source | confluence |
| - location | north of Livermore |
| - elevation | 482 ft (147 m) |
| - coordinates | 37°42′20″N 121°45′18″W / 37.70556°N 121.75500°W |
| Mouth | Arroyo Mocho |
| - location | north of Dublin |
| - elevation | 348 ft (106 m) |
| - coordinates | 37°41′41″N 121°51′34″W / 37.69472°N 121.85944°WCoordinates: 37°41′41″N 121°51′34″W / 37.69472°N 121.85944°W |
Arroyo Las Positas is a 7.4-mile-long (11.9 km) westward-flowing watercourse in Alameda County, California, which originates from Arroyo Seco north of Livermore and empties into Arroyo Mocho in Dublin, California.