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(or orbital lamina) is a smooth, oblong bone plate which forms the lateral surface of the labyrinth of the ethmoid bone in the skull. The plate covers in the middle and posterior ethmoidal cells and forms a large part of the medial wall of the orbit.

It articulates above with the orbital plate of the frontal bone, below with the maxilla and the orbital process of palatine bone, in front with the lacrimal bone, and behind with the sphenoid.

Its name lamina papyracea is a literal description, as this part of the ethmoid bone is paper-thin and fractures easily. A fracture here could cause entrapment of the medial rectus muscle.