Route 125 is a minor state highway in northwestern Connecticut, running entirely within the town of Cornwall.

Route 125 is two lanes wide and is classified as a rural collector road for its entire length.

Route 125 was established from a previously unnumbered road in the 1932 state highway renumbering.

It originally ran from Jewell Street, where the town offices of Cornwall are located, to its current northern terminus at Route 128.

It was scheduled for cancellation in the 1962 Route Reclassification Act but it was ultimately decided to be retained in the state highway system.