Route 165 is a state highway in southeastern Connecticut running from Norwich to the Rhode Island state line in Voluntown, and continuing as RI Route 165.

Route 165 begins at an intersection with Route 2 in eastern Norwich and heads northeast into Preston. In Preston, it continues east through the town into Griswold. In Griswold, it continues generally east-northeast across Pachaug Pond and Glasgo Pond before continuing into Voluntown. In Voluntown, it heads northeast to overlap Route 49 and Route 138 in a triple concurrency. It turns east with Routes 49 and 138, then continues east in a concurrency with Route 138. After leaving Route 138, Route 165 continues east to the Rhode Island state line, meeting RI Route 165.

Route 165 was commissioned in 1932, running from Route 2 in Norwich to Route 138 in Voluntown, apparently on a different route around Pachaug Pond in Griswold. Between 1932 and 1936, it was rerouted to its current location crossing Pachaug Pond at its southern end. In 1947, it was extended to the Rhode Island state line. In 1960, a section in Norwich and Preston was rerouted from Long Society Road to its current location.

The entire route is in New London County.

Location	mi	km	Destinations	Notes
Norwich	0.00	0.00	Route 2 (East Main Street) – Colchester, Preston
Preston	5.16	8.30	Route 164 (Jewett City Road) – Ledyard, Jewett City
Griswold	10.15	16.33	Route 201 (Glasgo Road) – Hopeville, North Stonington
Voluntown	12.12	19.51	Route 49 south (Westerly Road) – North Stonington	Western terminus of Route 49 overlap
	12.20	19.63	Route 138 west (Jewett City Road) – Jewett City	Western terminus of Route 138 overlap
	12.59	20.26	Route 49 north (Ekonk Hill Road) – Sterling	Eastern terminus of Route 49 overlap
	13.69	22.03	Route 138 east (Rockville Road) – Rockville, RI	Eastern terminus of Route 138 overlap
	16.01	25.77	Route 165 east – Exeter	Continuation beyond Rhode Island state line
1.000 mi = 1.609 km; 1.000 km = 0.621 mi       Concurrency terminus