Washington Township is a township in Lycoming County, Pennsylvania. The population was 1,613 at the 2000 census. It is part of the Williamsport, Pennsylvania Metropolitan Statistical Area.

Washington Township is bordered by Clinton County to the west, Limestone Township to the northwest, Armstrong Township to the north, Brady Township to the northeast, and Union County to the east and south.

Washington Township was formed as part of Northumberland County in 1786. It originally extended from White Deer Hole Creek north to the West Branch Susquehanna River with its eastern boundary also formed by the west branch. The western limit was ambiguous, but most historians assumed that the western boundary followed a line that extended to the south opposite the mouth of Pine Creek in what is now eastern Clinton County. Washington Township is older than Lycoming County. Therefore it was one of the original townships in Lycoming County. Seven additional townships were created from land that was originally part of Washington Township. They are Armstrong, Bastress, Brady, Clinton, Limestone, Nippenose, and Susquehanna Townships. The township is named for the hero of the American Revolution and the 1st President of the United States, George Washington.

Historically, two trails of the native indigenous peoples ran along parts of White Deer Hole Creek in Washington Township. Settlers arrived by 1760, but fled in 1778 during the American Revolutionary War during The Big Runaway. They returned and the creek served as the southern boundary of Lycoming County and Washington Township when it was formed in 1795.

The Great Island Path was a major trail that ran north along the Susquehanna River from the Saponi village of Shamokin at modern Sunbury, fording the river there and following the west bank of the West Branch Susquehanna River north until White Deer Hole valley. The path turned west at Allenwood and followed White Deer Hole Creek until about the present location of Elimsport in Washington Township. There it headed northwest, crossed North White Deer Ridge and passed west through the Nippenose valley, then turned north and crossed Bald Eagle Mountain via McElhattan Creek and ran along the south bank of the river to the Great Island (near the present day city of Lock Haven).

Beginning with the first settlers, much of the land along White Deer Hole Creek in Washington Township was slowly cleared of timber. Small sawmills were built in the 19th century, and a much larger lumber operation was run by the Vincent Lumber Company from 1901 to 1904. They built a Template: 3 ft 6 in narrow gauge railroad from Elimsport 5 miles (8 km) west into timber, and a line east to Allenwood in Union County and the Reading Railroad there. The lumber railroad ran parallel to the creek, with the end of the track near the Fourth Gap. It was incorporated on 24 June 1901 (around the time of construction) as the "Allenwood and Western Railroad." The lumbering operation ceased in 1904 when the forests were gone. The railroad was torn up, and its one second-hand Shay locomotive was moved to the Vincent Lumber Company operation at Denholm (in Juniata County).

From 1900 to 1935, much of what is now Tiadaghton State Forest was purchased by Pennsylvania from lumber companies that had no further use for the clear-cut land. In the 1930s there were seven Civilian Conservation Corps camps to construct roads and trails in the forest.

Small-scale lumbering continues in the Washington Township, but the forest is certified as well-managed "in an environmentally sensitive manner" and lumber from it qualifies for a "green label". A sawmill owned and operated by the Amish of the region is on Pennsylvania Route 44 in Elimsport. It burned down on 10 May 2006 (causing $500,000 in damages) but was expected to be back in operation in a month. Despite this small-scale lumbering, as of 2006 the forests have grown back and are mixed oak, with blueberry and mountain laurel bushes. White Deer Hole Creek and its tributaries also have stands of hemlock and thickets of rhododendron along them.