In geometry, a decahedron is a polyhedron with ten faces. There are 32300 topologically distinct decahedra,^[1][2] and none are regular, so this name does not identify a specific type of polyhedron except for the number of faces.

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Some decahedra have regular faces:

• Octagonal prism (uniform 8-prism)
• Square antiprism (uniform 4-antiprism)
• Square cupola (Johnson solid 4)
• Pentagonal bipyramid (Johnson solid 13, 5-bipyramid)
• Augmented pentagonal prism (Johnson solid 52)

The decahedra with irregular faces include:

• Pentagonal trapezohedron (5-trapezohedron, antiprism dual) – often used as a die in role playing games, known as a d10
• Truncated square trapezohedron
• Enneagonal pyramid (9-pyramid)
• Ten of diamonds decahedron - a space-filling polyhedron with D_2d symmetry.