Ulubey, formerly Göbek, is a town and district of Usak Province in the inner Aegean Region of Turkey.

The district is famous for Ulubey Canyon and the ruins of Blaundus which was a Roman episcopal city in Asia Minor, presently Anatolia (Asian Turkey), and is now a Latin Catholic titular bishopric.

Ulubey Canyon Nature Park is a nature park in the Ulubey and Karahalli districts of Usak Province. The canyon is the second longest in the world after the Grand Canyon in the United States. The park provides suitable habitat for many species of animals and plants and is being developed as a centre for ecotourism. Ulubey Canyon covers an area of 119 hectares (290 acres). It is 100-500 m (330-1,640 ft) wide and 135-170 m (443-558 ft) deep, with a total length of 40-45 km (25-28 mi).

The streams Ulubey Creek and Banaz Creek (tributaries of Büyük Menderes River) run through the Ulubey Canyon. The main canyon along both creeks has tens of big lateral canyons. The walls of the canyon are 10-30 m (33-98 ft) and 50-55 m (164-180 ft) high. At least three terraces are visible in the canyon walls. In addition, there are many conical karstic hills along the canyon.

Plants growing in the nature park include the Turkish pine (Pinus brutia), rockrose (Cistus), oak (Quercus ithaburensis), Turkey oak (Quercus cerris), salt cedar (Tamarix), sumac (Rhus), hackberry (Celtis), broom (Genista), mullein (Verbascum), milkvetch (Astragalus) and wild marjoram (Origanum).