  Non-classical photon sources are a crucial resource for distributed quantum
networks. Photons generated from matter systems with memory capability are
particularly promising, as they can be integrated into a network where each
source is used on-demand. Among all kinds of solid state and atomic quantum
memories, room-temperature atomic vapours are especially attractive due to
their robustness and potential scalability. To-date room-temperature photon
sources have been limited either in their memory time or the purity of the
photonic state. Here we demonstrate a single-photon source based on
room-temperature memory. Following heralded loading of the memory, a single
photon is retrieved from it after a variable storage time. The single-photon
character of the retrieved field is validated by the strong suppression of the
two-photon component with antibunching as low as $g^{(2)}_{\text{RR|W=1}} =
0.20 \pm 0.07$. Non-classical correlations between the heralding and the
retrieved photons are maintained for up to $\tau_{\text{NC}}^{\mathcal R} =
(0.68\pm 0.08)$ ms, more than two orders of magnitude longer than previously
demonstrated with other room-temperature systems. Correlations sufficient for
violating Bell inequalities exist for up to $\tau_{\text{BI}} = (0.15 \pm
0.03)$ ms.
