The koteka, horim, or penis sheath is a phallocrypt or phallocarp traditionally worn by native male inhabitants of some (mainly highland) ethnic group in western New Guinea (West Papua/Irian Jaya) to cover their genitals. They are normally made from dried out gourd, Lagenaria siceria, although other species such as Nepenthes mirabilis, are also used. They are held in place by small loop of fiber attached to the base of the koteka and placed around the scrotum. There is a secondary loop placed around the chest or abdomen and attached to the main body of the koteka. Men choose kotekas similar to ones worn by other men in their cultural group. For example: Yali men favour a long, thin koteka, which help hold up the multiple rattan hoops around their waist. Men from Tiom wear a double gourd, help up with a strip of cloth, and use the space between the two gourds for carrying small items such as money and tobacco.

Many tribes can be identified by the way they wear their koteka. Some wear them pointed straight out, straight up, at an angle, or in other directions. The diameter of the koteka can also be a clue. Contrary to popular belief, there is little correlation between the size or length of the koteka and the social status  of the wearer. Kotekas of different sizes serve different purposes: very short kotekas are worn when working and longer and more elaborate kotekas are worn on festive occasions.

The koteka is made of specially grown gourd. Stone weights are tied to the bottom of the gourd to stretch it out as it grows. Curves can be made in it by the use of string to restrain its growth in whatever direction the grower wishes. They can be quite elaborately shaped in this manner. When harvested, the gourd is emptied and dried. It's sometimes waxed with beeswax or native resins. It can be painted and/or have shells, feathers, other decorations attached to it.