Evaporation is the conversion process of liquid water into vapor and the consequent transport of that vapor into the atmosphere. In vegetation systems, water vapor flux can emerge from two sources. Water vapor flux directly from soil, canopies, or free water surfaces is known as evaporation. On the other hand, water movement through plant roots, stems, and consequent evaporation into the atmosphere through foliage is termed transpiration. It is sometimes difficult to distinguish between these two processes in vegetated systems. Therefore, the term evapotranspiration (ET), which combines evaporation and transpiration, was coined. Water that evaporates from the surface to the atmosphere is lost and cannot be used anymore. Therefore, evapotranspiration is a significant component of water balance, along with precipitation, seepage, and surface flow. Hence, understanding ET is vital in order to optimize irrigated agriculture water use efficiency and manage natural ecosystems such as forests or grasslands. In the context of climate change and the growing interest in global climate models (GCMs), evapotranspiration plays a vital role as a boundary condition in atmospheric or soil water modeling. One of the pioneering studies on evaporation dates back to 1802 [1], where the roles of wind speed and vapor pressure deficit in the evaporation process were illustrated. Later studies elaborated on the governing factors influencing evaporation and transpiration, including solar radiation, air temperature, air humidity, wind speed, and plant characteristics [2,3]. The FAO used the Penman–Monteith ET model [4] to establish guidelines for crop irrigation, which became a world standard. This Special Issue (SI), entitled “Evapotranspiration Measurements and Modeling”, contains fifteen papers that cover various experimental, modeling, and remote sensing approaches.