Piatt Township is a township in Lycoming County, Pennsylvania. The population was 1,259 at the 2000 census. It is part of the Williamsport, Pennsylvania Metropolitan Statistical Area.

Piatt Township is bordered by Mifflin Township to the north, Woodward Township to the east, the West Branch Susquehanna River to the south, and Porter Township to the west.

Piatt Township was formed from part of Mifflin Township by the Pennsylvania General Assembly on 30 April 1857. The new township encompassed what was the southermost part of Mifflin Township. Piatt Township is named for William Piatt who has an associate judge in Lycoming County when the township was created.

Larrys Creek, which bisects Piatt Township, is named for Larry Burt, the first settler in the area, who lived near the mouth of the creek near what is now the hamlet of Larrys Creek. He traded with the indigenous peoples and according to tradition had a Native American wife. Larry Burt was already there when surveyors came through in 1769 (after the land was purchased in the first Treaty of Fort Stanwix), but disappeared sometime soon after, perhaps moving west with the Native Americans who left the area.

Other settlers soon followed Larry Burt to the what it now Piatt Township. They settled along the banks of Larrys Creek near where the creek flows into the West Branch Susquehanna River. Peter Duffy was one of the most prominent of the early settlers. He settled with his family at the mouth of Larrys Creek in August 1784. Duffy's journey from County Kildare, Ireland was a long and difficult struggle. He left from Dublin in July 1775 during the early years of the American Revolution. Duffy was an acquaintance of Major John Pitcairn. Pitcairn was with the Royal Marines and was part of the British force that was occupying Boston, Massachusetts at the outset of the Revolution. Pitcairn was killed at the Battle of Bunker Hill. This left Peter Duffy with a bit of a problem. He no longer had a point of contact in the Thirteen Colonies.

Duffy and his family landed in Philadelphia in August 1775. After a short stay in the Philadelphia area, he and his family moved further inland to Lancaster County. The family spent seven years in the Lancaster area before moving to Coxestown, know known as Susquehanna Township, just north of Harrisburg in Dauphin County. The Duffy's owned a home along the banks of the Susquehanna River for about a year before it was flooded and accidentally burned in the winter of 1784. Peter Duffy did not lot this stop him. He gathered is family and migrated further still into the Pennsylvania frontier. The Duffy Family was joined by the Stewart Family on their trip from Dauphin County to Lycoming County. Both families settled down to the east of what is now Jersey Shore. The Stewarts settled on the southern side of the West Branch Susquehanna River in Nippenose Township and the Duffys settled on the opposite shore in Piatt Township.

Peter Duffy built his home near where the Great Shamokin Path crossed Larrys Creek. This path became and important road in the settlement of the West Branch Susquehanna River Valley. Early pioneers trekked up the road as they continued to move ever westward. Peter Duffy opened a inn that soon became an important stopping point for the pioneers. Sadly, Duffy was unable to enjoy his prominence for very long. Late one evening, while returning from a hunt, a pack of wolves attacked Peter Duffy along the Great Shamokin Path. Duffy was able to fend off the wolves and returned safely home, but the cold and the extreme effort he put into defeding himself left him weakened. He came down with a severe and fatal cold.

Duffy's widow Martha was left to manage the inn with the help of her children. Tragically soon after Peter's death, their first born son, James also died. James Duffy was attending a wedding party at Culbertson's Mill in Duboistown in February 1807 when he was accidentally killed. Marha Duffy was left with her four remaining children. Her second daughter, Catharine, had married and moved with her husband to Meadville in Crawford County. The oldest daughter, Mary Ann, took over management of the inn. Bernard operated the family owned sawmill, Margaret managed the Duffy family home, and Peter, the son, managed the family farm. These four Duffy children never married and spent the rest of their lives living together in the family home in Piatt Township.

The area of land along the West Branch and Larrys Creek was previously known as "Level Corner." Many of the early settlers were attracted to this area of fertile farmland. Isaac Smith migrated to Piatt Township, from Chester County. Smith was a millwright and farmer. Robert Covenhoven was another prominent early settler. He was a veteran of the American Revolution having fought at the Battles of Trenton and Princeton. Covenhoven had returned to the West Branch Valley just before the Big Runaway. Upon hearing of the approaching raiding Indians and Loyalist, Covenhoven rode west along the ridge of Bald Eagle Mountain to warn settlers at Fort Antes (opposite what is now Jersey Shore) and the western part of the valley. Covenhoven is listed as a Fair Play Man and one of the signers of the Tiadaghton Declaration of Independence. Following the Great Runaway Covenhoven continued to serve as a scout for the Patriot forces on the Pennsylvania Frontier. At the conclusion of the war he settled with his wife at Level Corner. They raised a family of three sons and five daughters. Covenhoven live a long life before dying at the age of 90. He is buried in Northumberland where he went to live with his daughter Nancy after his wife Mercy's death.