  We study higher-form symmetries in 5d quantum field theories, whose charged
operators include extended operators such as Wilson line and 't Hooft
operators. We outline criteria for the existence of higher-form symmetries both
from a field theory point of view as well as from the geometric realization in
M-theory on non-compact Calabi-Yau threefolds. A geometric criterion for
determining the higher-form symmetry from the intersection data of the
Calabi-Yau is provided, and we test it in a multitude of examples, including
toric geometries. We further check that the higher-form symmetry is consistent
with dualities and is invariant under flop transitions, which relate theories
with the same UV-fixed point. We explore extensions to higher-form symmetries
in other compactifications of M-theory, such as $G_2$-holonomy manifolds, which
give rise to 4d $\mathcal{N}=1$ theories.
