Anthocyanins from flowers of common lilac (Syringa vulgaris L.) of various color intensities and shades of lilac color from nine samples purchased at the Belgorod market were studied using reverse-phase high-performance liquid chromatography. To determine the structure of anthocyanins, we used the analysis of electronic absorption spectra recorded in the cuvette of a diode array detector and the analysis of mass spectra obtained by electrospray ionization with partial fragmentation. As a result, it was found that in all the studied samples the main component was delphinidin-3-rutinoside (84–90% by peak areas in the chromatogram). The level of cyanidin-3-rutinoside biosynthesis was significantly lower (6–19.6%). Among the minor compounds, delphinidin-3-glucoside and petunidin-3-glucoside were found. Among the unusual compounds, pyranoanthocyanin, built on the basis of delphinidin-3-rutinoside due to condensation with pyruvic acid, was found in a number of studied samples, but the reasons for its appearance have not yet been established. The total content of anthocyanins is low and amounts to 0.020–0.120 g per 100 g of fresh material (depending on the color intensity of the original plant material) in terms of cyanidin-3-glucoside. By drying flowers on a cut branch, air-dried material was obtained containing 0.100–0.300 g per 100 g of anthocyanins.