We present Quotebank, an open corpus of 178 million quotations attributed to the speakers who uttered them, extracted from 162 million English news articles published between 2008 and 2020. In order to produce this Web-scale corpus, while at the same time benefiting from the performance of modern neural models, we introduce Quobert, a minimally supervised framework for extracting and attributing quotations from massive corpora. Quobert avoids the necessity of manually labeled input and instead exploits the redundancy of the corpus by bootstrapping from a single seed pattern to extract training data for fine-tuning a BERT-based model. Quobert is language- and corpus-agnostic and correctly attributes 86.9% of quotations in our experiments. Quotebank and Quobert are publicly available at https://doi.org/10.5281/zenodo.4277311.