  This paper investigates the Casimir effect of a wedge and its holographic
dual. We prove that the displacement operator universally determines the wedge
Casimir effect in the smooth limit. Besides, we argue that the wedge Casimir
energy increases with the opening angle and test it with several examples.
Furthermore, we construct the holographic dual of wedges in AdS/BCFT in general
dimensions. We verify that our proposal can produce the expected Casimir effect
within smooth and singular limits. We observe that the Casimir energy density
of a wedge increases with the brane tension. Next, we discuss the wedge
contribution to holographic entanglement entropy and find it increases with the
opening angle, similar to the wedge Casimir energy. Finally, we briefly discuss
the holographic polygon in AdS$_3$/BCFT$_2$ and its generalization to higher
dimensions.
