The emission spectrum of OsN has been recorded in the 3000-13 000 cm(-1) region using a Fourier transform spectrometer. OsN molecules were excited in an osmium hollow cathode lamp operated with neon gas and a trace of nitrogen. Six bands observed in the 8000-12 200 cm(-1) region have been classified into three transitions, a (4)Pi(5/2)-X (2)Delta(5/2), b (4)Phi(7/2)-X (2)Delta(5/2), and b (4)Phi(5/2)-X (2)Delta(5/2) with the 0-0 band origins near 8381.7, 11 147.9, and 12 127.2 cm(-1), respectively. A rotational analysis of these bands provides the following equilibrium constants for the ground electronic state: omega(e) = 1147.9492(77) cm(-1), omega(e)x(e) = 5.4603(36) cm(-1), B-e = 0.493 381(55) cm(-1), alpha(e) = 0.002 753(38) cm(-1), and r(e) = 1.618 023(91) Angstrom. Ab initio calculations have been performed on OsN and the spectroscopic properties of the low-lying electronic states have been calculated. Our assignments are supported by these calculations. The ground state of OsN has been identified as a (2)Delta(i) state consistent with the observations for the isoelectronic IrC molecule [Jansson , Chem. Phys. Lett. 4, 188 (1969); J. Mol. Spectrosc. 36, 248 (1970)]. The 1 sigma(2)2 sigma(2)1 pi(4)1 delta(3)3 sigma(2) electron configuration has been proposed for the ground state and the configurations for the other low-lying electronic states have also been discussed. This work represents the first experimental or theoretical investigation of the electronic spectra of OsN.