| State: | HI |
| Type: | HI |
| Route: | 31 |
| Alternate Name: | Pi'ilani Highway |
| Map Custom: | yes |
| Map Notes: | Route 31 highlighted in red |
| Section1: | Kihei segment |
| Length Mi1: | 7.2 |
| Direction A1: | North |
| Terminus A1: | in Kihei |
| Direction B1: | South |
| Terminus B1: | Wailea Ike Drive in Wailea |
| Section2: | Kaupo segment |
| Length Mi2: | 22.4 |
| Direction A2: | West |
| Terminus A2: | near Kula |
| Direction B2: | East |
| Terminus B2: | in Haleakala Nat'l Park |
| Counties: | Maui |
| Previous Type: | HI |
| Previous Route: | 30 |
| Next Type: | HI |
| Next Route: | 32 |
Hawaii Route 31, also known as the Pi'ilani Highway, is a 38-mile road on the island of Maui in Maui County, Hawaii, United States.
The route begins in at an intersection with Hawaii Routes 310 and 311 in the East Maui town of Kihei. The highway formerly ran parallel to the coast all the way to the southern terminus of the Hana Highway (Route 360), until developments in Wailea and Makena blocked access. The Kihei section of the highway now terminates in Wailea, and the much longer Kaupo section, which is mostly a one-lane, winding road, is county-maintained as County Road 31, connects Route 37 near Kula to the Route 360 south of Hana (at the western border of Haleakala National Park).