Route 313 is a Connecticut state highway in the outer northwestern New Haven suburbs, running from Seymour to Woodbridge.

It heads briefly south along the Naugatuck River and underneath Route 8 without an interchange, then turns east across the Naugatuck River.

In Woodbridge, it continues southeast to end at an intersection with Route 243.

In 1936, the Woodbridge portion of the turnpike (Rimmon Road) was taken over by the state as SR 563.

These three unsigned state roads were combined into Route 313 in 1963 and has had no major changes since.