Muncy Creek (also known as Big Muncy Creek) is a tributary of the West Branch Susquehanna River in Sullivan County and Lycoming County, in Pennsylvania, United States. It is approximately long. The watershed of the creek has an area of . The creek's discharge averages at Sonestown, but can be up to a thousand times higher at Muncy. The headwaters of the creek are on the Allegheny Plateau. Rock formations in the watershed include the Chemung Formation and the Catskill Formation.
There are a number of lakes in the watershed of Muncy Creek, including Eagles Mere Lake, Highland Lake, and Beaver Lake. The creek was known as Occohpocheny to Native Americans. The area in its vicinity was settled in 1783. Various other industries and mills were constructed in the creek's vicinity from the late 18th century to the early 20th century. Wild trout naturally reproduce in part of Muncy Creek. Part of the creek is navigable by canoe.
Course
thumb|left|Muncy Creek in Muncy Creek Township
Muncy Creek begins in southeastern Laporte Township, Sullivan County, near its border with Davidson Township, Sullivan County. The creek flows southwest and then west for a short distance before reaching the border between Laporte Township and Davidson Township. It then turns southwest as it begins to follow this border. Shortly afterwards it turns northwest and begins to flow into a valley, then turns west and begins receiving very short tributaries from both sides. Examples of these include Rock Run and Lopez Pond Branch. After picking up Peters Creek, one such tributary, Muncy Creek turns southwest and passes the community of Nordmont, where the tributary Elklick Run flows into it. The creek then turns southwest and later west. Deep Hollow Run then enters the creek, which heads south away from the Laporte Township/Davidson Township border. Upon leaving behind the Laporte Township/Davidson Township border, the creek enters Davidson Township and heads west-southwest, passing a gauging station. After several miles, it reaches the community of Sonestown, where the tributary Big Run flows into it from the north. Muncy Creek then makes a sharp bend south and begins flowing parallel to U.S. Route 220. After a few miles, it passes the community of Muncy Valley and makes a sharp turn south, exiting Davidson Township.
Upon exiting Davidson Township, Sullivan County, Muncy Creek enters Lycoming County and flows along the border between Shrewsbury Township and Penn Township for several miles. It continues following U.S. Route 220 during this time, picking up a few tributaries, including Lick Run. The creek also passes by Glen Mawr and Tivoli during this stretch. Beyond the stretch, in Picture Rocks, the creek crosses Pennsylvania Route 864. Beyond the community, the creek continues south into Wolf Township, leaving its valley passing by the eastern edge of Hughesville. Some distance further on, the creek receives the tributary Sugar Run and some miles later leaves Wolf Township in a southwesterly direction. Upon exiting Wolf Township, the creek enters Muncy Creek Township, where Little Muncy Creek flows into it. Muncy Creek then turns northeast, crossing Pennsylvania Route 405 and turns southwest, crossing Interstate 180. The creek then receives the tributary Wolf Run and immediately afterwards empties into the West Branch Susquehanna River. Muncy Creek joins the West Branch Susquehanna River is upstream of its mouth. Other large tributaries of the creek include Lewis Creek, Rock Run, and Sugar Run. The watersheds of these tributaries have areas of , , and , respectively. Muncy Creek also has numerous minor tributaries. The osmotic pressure of the stream's waters at this location ranged from less than 1 up to 4 millios-moles per . The annual rate of precipitation near the creek ranges from . The headwaters of the creek are more than higher than its mouth. Muncy Creek's course winds significantly, but flows generally southwest. In general, rock formations consisting of sandstone and shale are found along much of the creek, while rock formations of limestone occur close to its mouth.
The soils in the valley of Muncy Creek are deep but relatively poor.
The channel of Muncy Creek is sinuous with high streambanks and the creek has cobble and gravel bars. The area of the creek's watershed upstream of Sonestown is .
There are a number of lakes in the watershed of Muncy Creek. The largest is Eagles Mere Lake, which has an area of . Hunters Lake has an area of and Highland Lake has an area of . Additionally, Beaver Lake (which has an area of ) is located in the watershed of the tributary Little Muncy creek. The name sometimes has been spelled "Muncey Creek".
Muncy Creek was known to the Native Americans as Occohpocheny. The creek experienced severe flooding in 1889. Wild trout naturally reproduce in the creek from Trout Run downstream to its mouth.
A total of 92 percent of assessed streams in the watershed of Muncy Creek are inhabited by trout. Of the inhabited streams, 82 percent are inhabited only by brook trout, nine percent are inhabited by only brown trout, and nine percent are inhabited by both brook trout and brown trout. A number of tributaries of the creek are designated as high-quality coldwater fisheries. These include Lick Run, Roaring Run, Rock Run, and Spring Run in Lycoming County and Big Run, Trout Run, and a number of others in Sullivan County.
Recreation
It is possible to canoe on Muncy Creek during snowmelts or shortly after heavier rainstorms. Although the creek is used for canoeing by locals, it is less popular for this use than the nearby Loyalsock Creek. Edward Gertler considers the creek to be especially good for novice canoers. He describes Muncy Creek as a "pleasing but generally mediocre mountain stream" in his book Keystone Canoeing. However, it is only possible to canoe on the creek downstream of the plateau of North Mountain. A total of of the creek is canoeable. The difficulty rating of Muncy Creek for canoeing ranges from 1+ to 2.