The thermal decomposition of furfural is investigated experimentally and through theoretical calculations at the CBS-QB3 level of theory. Furfural is a major product observed during biomass pyrolysis, but despite its importance there are many speculations about the thermal decomposition channels of this compound. To address these open questions new experiments are performed in a jet-stirred reactor at atmospheric pressure and temperatures ranging from 900 to 1100 K with a furfural inlet mole fraction of 0.005 and He as diluent. The residence time is set to 2 s. The main products observed by GC analysis are CO, CO2, α-pyrone, furan, 3-furaldehyde, propyne, propadiene, acetylene, methane and benzene. Small amounts of other aromatics, e.g. toluene, styrene, benzaldehyde and phenol are observed as well. Theoretical calculations at the CBS-QB3 level are used to extend the furfural potential energy surface and to identify possible reaction pathways to the observed products. The unimolecular non-radical decomposition channel through α-pyrone as proposed in literature is confirmed as the main channel, but carbene pathways are found to make small contributions as well. Furthermore, pericyclic reactions are suggested to contribute to the molecular elimination of CO in open-chain molecules and Diels Alder reactions are found to be important for the formation of CO2 and aromatics. Finally, even radical chemistry initiated by homolytic scission of the approximately 380 kJ/mol strong C-H bond in the furfural carbonyl group has a non-negligible influence.