Connecticut's 12th State Senate district elects one member of the Connecticut State Senate. The district consists of the towns of Branford, North Branford, Durham, Guilford, Killingworth, and Madison. Its current senator is Christine Cohen. The district boundaries established after the 2010 census are the same as those established after the 2000 census.
At this point redistricting caused Fairfield County to be represented in the Senate by the 25th and 26th district.