Mifflin Township is a township in Lycoming County, Pennsylvania, United States. The population was 1,145 at the 2000 census. It is part of the Williamsport, Pennsylvania Metropolitan Statistical Area.

Mifflin Township is bordered by Cogan House Township to the north, Anthony Township to the east, Piatt Township to the south, Porter Township to the southwest, and Watson and Cummings Townships to the west. Mifflin Township surrounds the borough of Salladasburg.

Mifflin Township was formed in 1803 by dividing [Old] Lycoming Township. It is named in honor of Thomas Mifflin the first governor of Pennsylvania.

When colonial settlers first arrived in what is now Mifflin Township they were outside the western boundary of what was then the Province of Pennsylvania. These settlers were not under the jurisiction or protection of any type from any of the Thirteen Colonies. They became known as the Fair Play Men. These men established their own form of government, known as the "Fair Play System," with three elected commissioners who ruled on land claims and other issues for the group. In a remarkable coincidence, the Fair Play Men made their own Declaration of Independence from Britain on 4 July 1776 beneath the "Tiadaghton Elm" on the banks of Pine Creek.

Mifflin Township is located within the Larrys Creek watershed. This area was densely covered with trees and brush until about 1790 when the first settlers attempted to clear some of the land that surrounds Larrys Creek. John Murphy was the first settlers to establish a permanent homestead. He cleared some land along the creek and built a home. His daughter, Sarah, is thought to have been the first white child to have been born in Mifflin Township. Murphy was soon followed by other settlers who also built cabins, cleared some land for farming and built sawmills. Lumber was soon to become the dominant industry in Mifflin Township.

As timber and lumber became a major industry in the mid-19th century, Larrys Creek, in Mifflin Township, was a source of power for sawmills and other mills. The first sawmill on the creek was built in 1799. The relatively low flow of water in the creek did not allow rafts of logs to be floated downstream to the river and the lumber boom at Williamsport.

This and the lack of logging railroads along the creek lead to the development of many small sawmills. Twelve sawmills were on the Second Fork, six on the First Fork, one each on Canoe Run and the rest were on Larrys Creek itself. By 1903 just two mills were still standing and only one of those was operating.

Lumbering removed the tree trunks, but left many flammable limbs, branches, and stumps behind. On May 2, 1872 a large forest fire destroyed the villages of Carter and Gould, 6 miles (10 km) north of Salladasburg on Larrys Creek in Mifflin Township. There are large tracts of second growth forest and small lumber companies still operate in the township today.