The PANACEA Environment Spanish monolingual corpus was acquired in the framework of the PANACEA project (Platform for Automatic, Normalized Annotation and Cost-Effective Acquisition of Language Resources for Human Language Technologies), under the European Commission's Seventh Framework Programme. This corpus contains documents that were acquired from the web, were automatically detected to be in the Spanish language and were automatically classified as relevant to the “Environment” domain. It was constructed in the summer of 2011 using the Focused Monolingual Crawler (FMC) developed in the context of PANACEA. The corpus contains 46,225,624 tokens, excluding tokens in a) short (smaller than 10 tokens) paragraphs, b) paragraphs that were automatically classified as boilerplate and c) paragraphs that were automatically detected in a language other than Spanish. They are divided into a total of 26,009 documents that were crawled from 2,053 web sites. The dataset consists of the original crawled HTML files and the corresponding CesDoc XML files with basic metadata.