AbstractWe present two‐photon excitation luminescence experiments on carbon nanotubes which show the excitonic origin of the optical excitations. The two‐photon allowed exciton state, which has even parity under rotation about the U‐axis, is roughly 300 meV above the one‐photon active, odd‐parity state. This indicates exciton binding energies on the order of 400 meV for nanotubes with diameters around 8 Å. Ab‐initio calculations of the exciton wavefunctions and energies are in good agreement with our experimental results, confirming the predictions on the symmetry of the exciton states. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)