Franklin County is a county on the northern border of the U.S. state of New York. To the north across the Canada–United States border are the Canadian provinces of Quebec and Ontario, from east to west. As of the 2020 census, the county population was 47,555. Its county seat is Malone. The county is named in honor of the United States Founding Father Benjamin Franklin. The county is part of the North Country region of the state.

Franklin County comprises the Malone, NY Micropolitan Statistical Area. Much of Franklin County is within Adirondack Park. Within the border of the county is the St. Regis Mohawk Reservation, or Akwesasne in the Mohawk language. Its population was nearly 3,300 in the 2010 census. The people are linked by community and history with the Mohawk of the Akwesasne reserve across the river, spanning the border of Quebec and Ontario. The Mohawk have had authority under the Jay Treaty to freely cross this international border.

This area was long occupied by Iroquoian-speaking peoples. In historic times, a group of primarily Mohawks established a village south of colonial Montreal across the St. Lawrence River; they had been trading with French colonists and many had converted to Catholicism. They were the easternmost nation of the Iroquois League of Five Nations, known in their language as the Haudenosaunee.

After the English conquered the Dutch in the New York area, they established counties in 1683, in the eastern part of New York province and what is now Vermont. Both groups had settled primarily in Albany and along the Hudson River, a major waterway linking the upriver fur trade with the market of Manhattan. The first counties were very large in geographic area, taking in low-density populations. Gradually new counties were formed as colonial settlement increased, but most settlers stayed east of the middle of the Mohawk Valley, as the Iroquois nations controlled the lands beyond that. Historically, the French, Dutch and English all traded with the Mohawk, the easternmost of these nations.

The area of the present Franklin County was part of Albany County when it was established in 1683. This was an enormous county, including the northern part of what became New York State as well as all of the present state of Vermont and, in theory, extending westward to the Pacific Ocean. This county was reduced in size on July 3, 1766, by the creation of Cumberland County, and further on March 16, 1770, by the creation of Gloucester County, both containing territory now in Vermont. On March 12, 1772, what was left of Albany County was split into three parts, one remaining under the name Albany County. Charlotte County contained the eastern portion.

In 1784, the name "Charlotte County" was changed to Washington County to honor George Washington, the American Revolutionary War general and later President of the United States of America.

In 1788, Clinton County was split off from Washington County. It comprised a much larger area than the present Clinton County, including several other counties or county parts of the present New York State.

Following the American Revolutionary War, the United States forced the Six Nations of the Haudenosaunee, or Iroquois Confederacy, to cede most of their lands in New York and Pennsylvania, as most had been allies of Great Britain, which had lost to the new United States. After the war, New York State sold off 5 million acres of former Iroquois territory at very low prices, seeking to attract settlers to develop farms and businesses. Land speculators quickly took advantage of the sales. Franklin County was part of the huge speculative Macomb's Purchase of 1791.