We present the integrated Hα emission line profile for 157 H ii regions in the central 3.4 × 3.4 arcmin2 of the galaxy M83 (NGC 5236). Using the Fabry–Perot interferometer GHαFaS, on the 4.2-m William Herschel Telescope on La Palma, we show the importance of a good characterization of the instrumental response function for the study of line profile shapes. The luminosity–velocity dispersion relation is also studied, and in the log(L)–log(σ) plane we do not find a linear relation, but an upper envelope with equation log(LHα) = 0.9 log(σ) + 38.1. For the adopted distance of 4.5 Mpc, the upper envelope appears at the luminosity L= 1038.5 erg s−1, in full agreement with previous studies of other galaxies, reinforcing the idea of using H ii regions as standard candles.