The Saw Kill is a 14.3-mile-long (23.0 km) tributary of the Hudson River, called the Metambesem by the Algonquin people of the area and sometimes called Sawkill Creek today. It rises in the town of Milan and drains a 22-square-mile (57 km²) area of northwestern Dutchess County, New York, that includes most of the town of Red Hook to the west and part of Rhinebeck to Red Hook's south.

It flows predominantly through forests and farmland. Just above its mouth, it descends more steeply through a wooded area with several waterfalls into South Tivoli Bay, between the Montgomery Place estate and Bard College, which uses the stream as both its primary water source and for disposal of its treated wastewater. In the 1840s, the owners of those properties made an agreement to prevent development along the stream, one of the earliest such conservation measures in American history.

The Saw Kill at first descends rapidly through the hills in Milan and eastern Red Hook where it rises. As those hills level out, it then meanders slowly across the flatter, more developed areas closer to the village of Red Hook, then at Annandale-on-Hudson once again descends rapidly to its mouth.

The Saw Kill rises on the slopes of an unnamed hill, just east of Broadview Lane in the town of Milan, at an elevation of approximately 690 feet (210 m) above sea level. It flows southwesterly through forested land for its first half-mile (1 km), descending 140 feet (43 m) as it does, until it reaches a small farm pond at the edge of some cleared land and turns to the northwest as it flows out. Over its next mile (1.6 km), crossing more fields, it gradually bends southwest again until it flows under a farm road and, its uppermost crossing, and reaches another, larger farm pond roughly a thousand feet (300 m) east of Milan Hill Road (Dutchess County Route 54), having lost another 50 feet (15 m) in elevation.

From the pond's outlet the Saw Kill flows first westerly, then turning strongly to the south southwest as it enters a wooded ravine closely paralleling Milan Hill Road for the next 1,800 feet (600 m). By the time it reaches the swampy areas where it flows under New York State Route 199 (NY 199), the uppermost public crossing of the stream, it has dropped to 400 feet (120 m) above sea level. Just past the highway, it bends to the west and runs roughly parallel to it.

For its next mile the Saw Kill widens its distance from the highway, flowing into another small farm pond, behind an auto-body shop, Milan's fire garage and another farm, crossing under two more farm roads in the process. After the last one, a covered bridge, it flows into another farm pond approximately 300 feet (100 m) long, turning north then west. At its outlet it turns north again where it soon flows under both Old Mill Road and NY 199 again through a long culvert at the hamlet of Rock City. North of this it flows into a small unnamed lake, 330 feet (100 m) above sea level, where it receives an unnamed tributary from the northeast. It exits that lake flowing to the west southwest again, crossing under Sawmill Road adjacent to its junction with Rock City Road and then, 150 feet (50 m) downstream, under NY 199 again, as both enter the town of Red Hook.

After this crossing, the Saw Kill flows roughly west through some swampy areas along the Rhinebeck town line for the next half-mile, in a wooded corridor south of a golf course. After receiving the Sepasco Lake outlet stream from the south, it bends northwest again, into a small lake. At the end of the lake a small private footbridge crosses, then the stream bends and descends 90 feet (27 m) to 240 feet (73 m) in elevation through a series of cascades alongside Oriole Mills Road to Camp Rising Sun.

The Saw Kill then flows generally north through level ground for its next mile, beginning to meander as it passes Sky Park Airport. Just short of NY 199, it receives its only named tributary, the Lakes Kill, from the north, and turns west again, following the highway to the south for 600 feet (200 m), before crossing under it for the fourth and final time. From there it distances itself from the road as it takes a more northwesterly heading.