DNA methylation is the process of adding a methyl group to a DNA molecule, often changing how the molecule interacts with other cellular factors. Methylation mainly occurs at cytosines in humans, often in the context of a cytosine followed by a guanine (CpG). Epigenome-wide association studies (EWAS) seek to understand the link between DNA methylation patterns at thousands or millions of CpG sites across the genome to various traits and exposures. In recent years, the increase in availability of DNA methylation measures in population-based cohorts and case-control studies has resulted in a dramatic increase in the number of EWAS being performed and published. To make this rich source of molecular data more accessible, we have manually curated a database of CpG-trait associations (with p<1x10-4) from published EWAS, each assaying over 100,000 CpGs in at least 100 individuals. The database currently contains over 500,000 CpG associations for more than 150 EWAS. It is accompanied by a web-based tool and R package that allow these associations to be easily queried. In the near future, we hope this database will be extended to include genome-wide EWAS summary statistics, including over 200 million associations from over 500 EWAS of the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort (N~900). This database will give researchers the opportunity to quickly and easily query EWAS associations to gain insight into the molecular underpinnings of disease as well as the impact of traits and exposures on the DNA methylome. The EWAS Catalog is available at: http://www.ewascatalog.org.