This is a list of early settlers of Marietta, Ohio, the first permanent settlement created by United States citizens after the establishment of the Northwest Territory in 1787. The settlers included soldiers of the American Revolutionary War and members of the Ohio Company of Associates.

The first group of these early settlers is sometimes referred to as "the forty-eight" or the "first forty-eight", and also as the "founders of Ohio". These first forty-eight men were carefully chosen and vetted by several of the co-founders of the Ohio Company of Associates, Rufus Putnam and Manasseh Cutler, to ensure not only men of high character and bravery, but also men with proven skills necessary to build a settlement in the wilderness. George Washington said of them: "I know many of the settlers personally, and there never were men better calculated to promote the welfare of such a community." General Lafayette of France, who fought with the Americans during the Revolution, visited Marietta on his US tour during May 1825 [1] and described these pioneers and former officers: "They were the bravest of brave. Better men never lived." The historian David McCullough noted that these pioneers were: "characters of historic accomplishment who were entirely unknown to most Americans".

Under the leadership of Rufus Putnam, two parties of pioneers comprising the first forty-eight men departed New England, cutting trails westward through the mountains during an uncommonly severe winter. One party departed from the towns of Ipswich, Massachusetts and Danvers, Massachusetts on December 3, 1787; the other party departed from Hartford, Connecticut on January 1, 1788. The pioneers crossed the mountains and met at Sumrill's Ferry (present-day West Newton, Pennsylvania) on the Youghiogheny River. During the bitterly cold winter, the men built two flatboats, the forty-five-ton Adventure Galley (also known as the Mayflower, in honor of their Pilgrim ancestors) and the three-ton Adelphia. They also built three log canoes. This small fleet of boats carried the pioneers down the Youghiogheny River to the Monongahela River, and then to the Ohio River, and onward to the Ohio Country and the Northwest Territory. They arrived at their final destination, the mouth of the Muskingum River at the confluence of the Ohio and Muskingum rivers, on April 7, 1788.