Alexandria Bay is a village situated in Jefferson County, New York, within the town of Alexandria. It lies in the Thousand Islands region of northern New York, positioned on the south bank of the Saint Lawrence River near the international border with Canada. The community serves as a local hub in this scenic area, bordered by Keewaydin State Park to the southwest and connected to the broader regional network via major highways.

Settlement in the area began around 1817, with approximately 25 dwellings established by 1836. The village played a role in regional history, notably hosting the Battle of Cranberry Creek in 1813 during the War of 1812. During its heyday as a late nineteenth and early twentieth-century resort, access was primarily via steamer from Clayton or rail connections at Redwood. Several local properties, including the George C. Boldt Yacht House and Holland Library, are listed on the National Register of Historic Places.

The village is defined by its historic architecture and proximity to Heart Island, home to Boldt Castle. This twelve-room mansion was built by George C. Boldt as a testament to his love for his wife, Louise, but construction halted in 1904 after her death. The castle complex, featuring eleven buildings in the Rhineland style, was acquired by the Thousand Islands Bridge Authority in 1977 and subsequently restored. The area also features the Cornwall Brothers' Store and Ingleside as significant architectural landmarks.

Visitor appeal peaks during late spring, summer, and early fall when vacationers and boaters flood the area. The village hosts Bill Johnston's Pirate Days every August, a ten-day festival featuring professional pirate performances and educational displays on the Golden Age of Piracy. Tourist activities include daily boat tours of the bay and river, with ferries providing hourly access to Boldt Castle. The influx of visitors significantly boosts the local economy during these warmer months.

As of the 2020 census, the population was 924, though it exceeds 15,000 during peak tourist seasons. The total value of exports reached $6.73 billion in 2020. Transportation access includes New York State Routes 12 and 26 intersecting at the village's only stoplight, with Interstate 81 located four miles southwest. Maxson Airfield serves general aviation needs, while public transit is unavailable within the small village limits.