This document defines the Missing Migrants Project’s methodological framework to serve as a guide for institutions interested in contributing relevant data, such as medical examiners, police departments, immigration authorities, as well as non-governmental actors working with migrants. For this reason, this document provides background information on IOM’s Missing Migrants Project data and describes the definitions and variables used for data collection. The main objective of these guidelines is to improve data collection within the Missing Migrants Project framework and thus to increase awareness about migrant fatalities in underreported regions globally.