The falx cerebri (also known as the cerebral falx) is a large, crescent-shaped fold of dura mater that descends vertically into the longitudinal fissure to separate the cerebral hemispheres. It supports the dural sinuses that provide venous and CSF drainage from the brain. It is attached to the crista galli anteriorly, and blends with the tentorium cerebelli posteriorly.

The falx cerebri is often subject to age-related calcification, and a site of falcine meningiomas.

The falx cerebri is named for its sickle-like shape.

The falx cerebri is a strong, crescent-shaped sheet of dura mater lying in the sagittal plane between the two cerebral hemispheres. It is one of four dural partitions of the brain along with the falx cerebelli, tentorium cerebelli, and diaphragma sellae; it is formed through invagination of the dura mater into the longitudinal fissure between the cerebral hemispheres.

Anteriorly, the falx cerebri is narrower, thinner, and may have a number of perforations. It is broader posteriorly.

The falx cerebri attaches anteriorly at the crista galli (proximally to the cribriform plate and to the frontal and ethmoid sinuses).

Posteriorly, it blends into the upper surface of the cerebellar tentorium.

Its convex superior margin is attached to the internal surface of the skull on either side of the midline. This attachment runs as far back as the internal occipital protuberance (the latter representing its posterior-most point of attachment); the superior sagittal sinus runs in the cranial groove between the falx cerebri's two attachments.