Technical Abstract: Precision agriculture is a new farming practice that has been developing since late 1980s. It has been variously referred to as precision farming, prescription farming, site-specific crop management, to name but a few. There are numerous definitions for precision agriculture, but the central concept is to identify within-field variability and manage that variability. More specifically, precision agriculture uses a suite of electronic sensors and spatial information technologies, such as Global Positioning Systems (GPS), Geographic Information Systems (GIS) and remote sensing, to map within-field soil and crop growth variability and to optimize farming inputs (i.e., fertilizers, pesticides, seeds, and water) to the specific conditions for each area of a field with the aim to increase farm profits and reduce environmental impacts. To automatically implement the concept of precision agriculture, the following four main steps are generally involved: 1) measuring spatial variability; 2) analyzing data and making decisions; 3) implementing management decisions; and 4) evaluating economic and environmental benefits. This chapter provides an overview of the major technologies involved in precision agriculture, including GPS, soil sensors, crop sensors, wireless technology, yield monitors, remote sensing, GIS, and variable rate technology. The emphasis is put on the principles and practice of these technologies for precision agriculture operations.