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).

The entire route is in Maui County.

Location	mi	km	Destinations	Notes
Kihei	0.0	0.0	Route 310 north (Kihei Road) / Route 311 north – Kahului, Airport, Lahaina	Southern termini of Routes 310 and 311
Wailea	7.2	11.6	Wailea Ike Drive west – Wailea, Makena	End state maintenance
Gap in route
​	16.0	25.7	Route 37 north (Kula Highway)	Southern terminus of Route 37; begin county maintenance
​	25.3	40.7	Begin one-lane roadway
Kalepa Gulch	38.4	61.8	Kalepa Bridge
Haleakala National Park	38.4	61.8	Route 360 west (Hana Highway)	Continues east as Route 360
1.000 mi = 1.609 km; 1.000 km = 0.621 mi

• List of state highways in Hawaii
• List of highways numbered 31

Media related to Hawaii Route 31 at Wikimedia Commons