New York State Route 3A (NY 3A) is a county-maintained state highway in Jefferson County, New York, in the United States. The route is an alternate route of NY 3 between the village of Deferiet and Fargo, a hamlet within the town of Wilna. While NY 3 veers south to serve the village of Carthage, NY 3A follows a direct east–west alignment between the two communities. The eastern half of the route passes through the Fort Drum limits. All of NY 3A is co-designated as County Route 36 (CR 36) and is co-signed as such.