Electronic discovery (e-discovery) is an integral component of legal informatics, touching on everything from search and artificial intelligence to design and legal services transformation. Any discussion of electronic discovery must begin with an explanation of its relevance to legal work. E-discovery – also known as “ediscovery” or, somewhat datedly, “eDiscovery” – is the discovery in legal proceedings of evidence in an electronic format. Due to the nature of modern technology, e-discovery encompasses an overwhelming majority of evidence, such that e-discovery and other forms of discovery have become virtually synonymous. As such, legal discovery is now fraught with issues concerning how information is stored, retrieved, exchanged, and generally made accessible to parties during legal proceedings. A common challenge for attorneys is what to do with a multi-terabyte collection of evidence that consists of millions of documents across hundreds of file types, with only a matter of months before their first depositions. The best solutions to this kind of increasingly common challenge will include recourse to big data and machine learning, which are discussed in this chapter.