The first spectra of the A 2Π3/2 ← X 2Π3/2 electronic transition of BrO using Fourier transform ultraviolet spectroscopy are obtained. Broadband vibrational spectra acquired at 298 ± 2 K and 228 ± 5 K, as well as high-resolution rotational spectra of the A ← X 7,0 and 12,0 vibrational bands are presented. Wavenumber positions for the spectra are obtained with high accuracy, and cross section assignments are made, incorporating the existing literature. With 35 cm-1 (0.40 nm) resolution the absolute cross section at the peak of the 7,0 band is determined to be (1.58 ± 0.12) × 10-17 cm2 molecule-1 at 298 ± 2 K and (1.97 ± 0.15) × 10-17 cm2 molecule-1 at 228 ± 5 K. BrO dissociation energies are determined with a graphical Birge−Sponer technique, using Le Roy−Bernstein theory to place an upper limit on the extrapolation. From the ground-state dissociation energy, D0‘‘ = 231.0 ± 1.7 kJ/mol, the heat of formation of BrO(g) is calculated, ΔfH°(0 K) = 133.7 ± 1.7 kJ/mol and ΔfH°(298.15 K) = 126.2 ± 1.7 kJ/mol. Cro...