relatively small number of transnational firms have come to wield a high degree of influence within the global food system. Recent years have seen firms all along agrifood supply chains merge and acquire one another, to form giant 'mega-companies' that are central players in what can only be described as a profound reconfiguration of the world food economy. This process is happening in markets for farm inputs, agricultural commodity trading, and food processing and retail [1][2][3] . In parts of the global food system where just a few giant firms control a large share of the marketplace, these firms can influence the types of seeds farmers plant, what crops are grown, what breeds of livestock are raised and in what types of facilities, working conditions for food system workers, and the types and prices of food items that appear on grocery store shelves, to name just a few examples.There is long-standing concern that powerful firms in concentrated markets are more incentivized to advance the short-term interests of their shareholders rather than the public good 4,5 , a concern that extends to food systems. Civil society groups worry that concentrated agrifood firms might pursue profit maximization strategies in ways that undermine the livelihoods of small-scale producers, push up prices, limit product choices and damage the environment. As preparations are underway for the 2021 UN Food Systems Summit (UNFSS), which has goals of making food systems more equitable, healthy and sustainable, civil society groups have expressed concern that the Summit agenda does not sufficiently focus on the implications of corporate power in food systems 6 . This relative neglect is especially puzzling in the context of growing global concern about the potential harm from concentrated markets in other sectors, such as Big Tech. Because food systems are so important for multiple reasons-food is a basic need as well as a basic human right, food systems provide livelihoods for nearly a third of humanity, and food systems are intimately connected to ecosystems-it is imperative that we have a better understanding of the potential consequences of corporate concentration and power in the sector.This Perspective examines the implications of corporate power in one highly concentrated sector-the global seed and agrochemical industry-that has become more consolidated in recent years 7,8 . The merger of Dow and DuPont in 2015, which spun out a new agricultural input firm, Corteva Agriscience, was one of three major mergers that the agricultural seed and chemical industry saw in the 2015-2018 period. ChemChina purchased Syngenta in early 2016, shortly after the Dow-DuPont deal was announced, and in 2018 Bayer purchased Monsanto. What was already a highly concentrated industry dominated by what were known as the Big Six firms since the early 2000s is now dominated by just four large firms: Bayer, Corteva, ChemChina-Syngenta and BASF (which grew by purchasing assets the other firms sold to get their merger deals approved by regulators).Closer exam...