Port Jefferson is a village in Salem Township, Shelby County, Ohio, United States. The population was 371 at the 2010 census.
Port Jefferson had its start around the time the Miami and Erie Canal was extended to that point. The town site was platted in 1836. The village was incorporated in 1842.
Port Jefferson is located at 40°19′50″N 84°05′28″W.
According to the United States Census Bureau, the village has a total area of 0.19 square miles (0.49 km2), of which 0.17 square miles (0.44 km2) is land and 0.02 square miles (0.05 km2) is water.
As of the census of 2010, there were 371 people, 142 households, and 97 families living in the village. The population density was 2,182.4 inhabitants per square mile (842.6/km2). There were 158 housing units at an average density of 929.4 per square mile (358.8/km2). The racial makeup of the village was 100.0% White.
There were 142 households of which 31.7% had children under the age of 18 living with them, 53.5% were married couples living together, 12.7% had a female householder with no husband present, 2.1% had a male householder with no wife present, and 31.7% were non-families. 23.9% of all households were made up of individuals and 7% had someone living alone who was 65 years of age or older.