The Financial Entity Identification and Integration Challenge is a series of challenges to exploit the power of financial Big Data and computational methods over heterogeneous financial collections. A fundamental first-step that has to be overcome, in order to benefit from a wealth of financial Big Data, is the resolution of mentions or references to the same financial entity, across multiple heterogeneous collections. While the Legal Entity Identifier (LEI) is a good first step to create a unique identifier (and associated data) for each financial entity, there are many essential steps and additional challenges that must be addressed to fully benefit from the adoption of the LEI. The FEIII Challenge broadly encompasses tasks that occur in semi-structured text in the financial domain. The primary task we will examine is record linkage: Given a set of N reference identifier lists, align identifiers between the lists that refer to the same financial entity. Further tasks will incorporate the resolution of mentions or references from financial documents. Financial entity identification and integration is a challenge for all financial institutions and for all software companies that provide IT support to these institutions. The FEIII Challenge is sponsored by the Office of Financial Research (OFR) and the National Institutes of Standards and Technology (NIST).