Kentuck Knob (also known as the Hagan House) is a house in Stewart Township within Fayette County, Pennsylvania, United States. Designed by the architect Frank Lloyd Wright in the Usonian style, the residence was developed for I. N. Hagan, the owner of a local ice-cream firm, along with his wife Bernardine. It is built on the southern slope of a knoll known as Kentuck Knob, overlooking the Youghiogheny River gorge. The name of the house and knoll is derived from Little Kentuck, a hill in Fayette County named by an 18th-century settler who was planning to move to Kentucky. The house is designated as a National Historic Landmark.

I. N. and Bernardine Hagan had learned of Wright's work through Edgar J. Kaufmann, a businessman who had hired Wright to design the Fallingwater house in Fayette County. The Hagans purchased 79 acres (32 ha) of land near Uniontown, Pennsylvania, in July 1953 and asked Wright to design a Usonian home for them. Despite being busy with multiple other projects, Wright agreed to design a house at Kentuck Knob, which was completed in 1956. The Hagans lived at Kentuck Knob until 1986, when they sold the property to Peter Palumbo, Baron Palumbo. The house was damaged by a fire shortly afterward, and the Palumbo family renovated the house afterward. Kentuck Knob has been open to the public for tours since 1996, and a visitor center there was completed in 2003.

The estate, accessed by a driveway from Pennsylvania State Route 2010, includes approximately 8,800 trees and a sculpture garden for the Palumbo family's art collection. The house itself is made of redwood and locally-quarried stone, with an overhanging copper roof and two exterior terraces. It is laid out around a hexagonal floor plan, which consists of two wings that partially surround a courtyard, converging at a hexagonal core. The interior covers 2,300 square feet (210 m²) and consists of seven rooms in an open plan arrangement. The kitchen, within the house's core, is surrounded by a living room to the west and a dining room to the west. Extending northeast of the core are three bedrooms, which are partially embedded into the hillside. The house's carport, which includes an art studio, is attached to the bedroom wing.

Kentuck Knob is in Stewart Township, located within Fayette County in southwestern Pennsylvania, United States. It is located approximately 70 miles (110 km) southeast of Pittsburgh. The estate was originally owned by the Hagan family and spanned 79 acres (32 ha); it has been expanded over the years to more than 600 acres (240 ha). The estate is next to the Youghiogheny River, although the river gorge is not readily visible from the house due to the presence of trees. The building itself is on the southern slope of a hill also known as Kentuck Knob.

The house is accessed via a gravel driveway leading from Pennsylvania Route 2010 (PA 2010), which is cited as measuring 1⁄4 mile (0.40 km) or nearly 1⁄2 mile (0.80 km) long. It winds through some woods and passes above a waterfall called Cucumber Falls. In addition to the main house, the property includes a greenhouse, farmhouse, barn, and wooden sheds; the greenhouse was salvaged from the nearby Fallingwater. The site had originally been farmland, but after the Hagans acquired it, they planted about 8,800 trees on the hill. These included Canadian hemlock, pin oak, shellbark hickory, sugar maple, tulip poplar, white ash, and white oak specimens. Dogwoods were also planted along the driveway, though many of these specimens later died. There are numerous boulders on the estate, which are arranged to give the appearance that they had ended up there naturally, even though the boulders were installed when the house was built. The boulders, along with ferns and evergreen plants, create a Japanese garden–like setting around the house.

After the family of the British nobleman Peter Palumbo, Baron Palumbo, acquired the house, they added a sculpture meadow, which is accessed by a winding trail that connects to the visitor center. British products are sold in the visitor center. The meadow includes works by artists such as Harry Bertoia, Scott Burton, Anthony Caro, Andy Goldsworthy, Alvar Gullichsen, Allen Jones, Phillip King, David Nash, Claes Oldenburg, Eva Reichl, George Rickey, Ray Smith, Wendy Taylor, and Michael Warren. Other pieces in the sculpture garden include two graffitied pieces of the Berlin Wall, a restroom structure, English telephone kiosks, and a pissoir. The sculptures incorporate materials like granite, steel, and wood, complementing the design of the main house. Aside from the sculptures, the landscape retains most of its original Hagan-era design.

The Sugarloaf Knob mountain is southeast of the house, while the Fort Necessity National Battlefield is to the southwest. In addition, a conservation easement for Ohiopyle State Park abuts the estate. Kentuck Knob is one of four buildings in southwestern Pennsylvania designed by Frank Lloyd Wright. The others are Fallingwater, a 7-mile (11 km) drive to the northeast, as well as Duncan House and Lindholm House at Polymath Park in Acme, Pennsylvania. Aside from Fallingwater, Kentuck Knob is the only other house in Fayette County that Wright designed.

The name originates from David Askins, a settler who wanted to move to Kentucky in the late 18th century before moving to a hill in Fayette County, which he called Little Kentuck. The Askins site, formed through the merger of the Mitchell, Morris, and Thorpe families' farms, later became Stewart Township's Kentuck District. Because the area is mountainous, it has remained largely undeveloped over the years. Just before the Hagan family bought the site, it was occupied by two Eastern European immigrants, Donath and Anna Peles, who had lived there since World War I.