Route 178 is a Connecticut state highway in the northern suburbs of Hartford, running from Bloomfield to Windsor.

The road heads generally east towards Bloomfield center, shifting to Mountain Avenue after 0.7 miles (1.1 km), then intersecting with Route 189 in the town center a mile later.

The route shifts to Wintonbury Avenue about 1.7 miles (2.7 km) later using a short segment of School Street.

After intersecting with Route 187, it soon enters the town of Windsor, becoming Park Avenue.

[1] Route 178 was commissioned in 1932, running from the intersection of School Street and Park Avenue in Bloomfield to its current eastern terminus.