  Quantum emitters in solid-state materials are highly promising building
blocks for quantum information processing and communication science. Recently,
single-photon emission from van der Waals materials has been reported in
transition metal dichalcogenides and hexagonal boron nitride, exhibiting the
potential to realize photonic quantum technologies in two-dimensional
materials. Here, we report the observation of single-photon generation from
exfoliated and thermally annealed single crystals of van der Waals
{\alpha}-MoO3. The second-order correlation function measurement displays a
clear photon antibunching, while the luminescence intensity exceeds 100
kcounts/s and remains stable under laser excitation. Also, the zero-phonon
lines of these emitters are distributed in a spectrally narrow energy range.
The theoretical calculation suggests that an oxygen vacancy defect is a
possible candidate for the observed emitters. Together with photostability and
brightness, quantum emitters in {\alpha}-MoO3 provide a new avenue to realize
photon-based quantum information science in van der Waals materials.
