Neutron-rich light nuclei and their reactions play an important role for the creation of chemical elements. Here, data from a Coulomb dissociation experiment on 20,21 N are reported. Relativistic 20,21 N ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the 19 N(n, γ) 20 N and 20 N(n, γ) 21 N excitation functions and thermonuclear reaction rates have been determined. The 19 N(n, γ) 20 N rate is up to a factor of 5 higher at T < 1 GK with respect to previous theoretical calculations, leading to a 10 % decrease in the predicted fluorine abundance.