The nexus between water, energy and food (WEF) security is a critical component of human well-being, and billions of dollars are spent annually on investments intended to ensure that it is adequately addressed. A central concept throughout this guidebook is that the rural poor (i.e., those who benefit most from investments in agricultural productivity) will fare best if the underlying environmental determinants of water, energy, and food security—the WEF nexus—are protected and enhanced. The purpose of this guidebook is to provide a practical, spatially explicit, ecosystem-based framework for the design and management of land investments that deliver increased water, energy and food security. It also provides an implementation-oriented means of operationalizing an otherwise theoretical concept highlighted as a significant global risk and opportunity for integration. This publication is aimed primarily at those involved in strategic planning and allocation of domestic and foreign investments as well as international agencies supporting or evaluating investments in other countries.