Route 309 is a Connecticut state highway in the northwestern Hartford suburbs running from Canton to Simsbury.

Route 309 begins at an intersection with Route 179 in North Canton and heads southeast into Simsbury.

In Simsbury, it curves southeast and east to end at an intersection with Route 167.

[1] North Canton Road and West Simsbury Road was established as SR 909 in 1962 as part of the Route Reclassification Act.

[2] The entire route is in Hartford County.