Soil moisture is a key variable of the climate system. It constrains plant transpiration in many regions of the world, with various effects on the water, energy, and biogeochemical cycles. Also, it is a storage component for rainfall and radiation anomalies, inducing persistence in the climate system. Furthermore, it plays a key role in climate-change projections. In this chapter, we present the past understandings of the importance of soil moisture for the climate system and provide an analysis of the current perspectives for research in this field. Special attention is paid to the aspects of soil moisture–climate interactions under climate change condition.