Route 305 is a Connecticut state highway in the northern Hartford suburbs, running from Bloomfield to Windsor.

It crosses the town line about a mile later and heads generally southeast.

It crosses over Mill Brook and then has an interchange with I-91 (at Exit 37) about 1.4 miles (2.3 km) east of the town line.

[1] Prior to 1963, part of the route, from the Bloomfield line to Route 75, was an unsigned but state-maintained road known as SR 905 (which became a state road in 1959).

Initially, the state had planned to turn over SR 905 to Windsor but when the final decisions for the 1962 Route Reclassification Act were announced, it was instead retained in the state highway system, with the continuation in Bloomfield also taken over by the state.