Descriptions of complex feeding relationships among species in ecosystems first appeared more than a century ago, and the quantitative analysis of the network structure of “food webs” dates back several decades. Improvements in food-web data collection, analysis, and modeling, coupled with a resurgence of interdisciplinary research on the topology of many kinds of “real-world” networks, have resulted in renewed interest in ecological network structure. Recent research suggests that food webs display universal scale-dependent patterns in how trophic links and roles are distributed among species in ecological communities. The fundamental ways in which feeding interactions are organized appears to have become established very early in the history of multicellular life on earth. Understanding the principles that underlie robust food-web patterns represents an important frontier of ecological research.