This paper introduces Opencpop, a publicly available high-quality Mandarin singing corpus designed for singing voicesynthesis (SVS). The corpus consists of 100 popular Mandarinsongs performed by a female professional singer. Audio filesare recorded with studio quality at a sampling rate of 44,100 Hzand the corresponding lyrics and musical scores are provided.All singing recordings have been phonetically annotated withphoneme boundaries and syllable (note) boundaries. To demon-strate the reliability of the released data and to provide a baselinefor future research, we built baseline deep neural network-basedSVS models and evaluated them with both objective metrics andsubjective mean opinion score (MOS) measure. Experimentalresults show that the best SVS model trained on our databaseachieves 3.70 MOS, indicating the reliability of the providedcorpus. Opencpop is released to the open-source community WeNet, and the corpus, as well as synthesized demos, can befound on the project homepage.