We demonstrate an ultrabright narrow-band two-photon source at the 1.5 μm telecom wavelength for long-distance quantum communication. By utilizing a bow-tie cavity, we obtain a cavity enhancement factor of 4.06 × 104. Our measurement of the second-order correlation function G(2)(t) reveals that the linewidth of 2.4 MHz has been hitherto unachieved in the 1.5 μm telecom band. This two-photon source is useful for obtaining a high absorption probability close to unity by quantum memories set inside quantum repeater nodes. Furthermore, to the best of our knowledge, the observed spectral brightness of 3.94 × 105 pairs/(s&amp
MHz&amp
mW) is also the highest reported over all wavelengths.