Weeds significantly impact crop growth and productivity, posing a major challenge in Latin America, where agricultural productivity surged after the 1960s due to market regulation, economic openness, and land reform. Farmers heavily rely on herbicides as affordable weed control tools; however, repeated use of herbicides with a single action mode has led to herbicide-resistant weeds, threatening agricultural sustainability. This chapter examines agricultural productivity in Latin America, its importance to the region’s economy, and its role as a global food, feed, and bioenergy supplier. It also explores the regional climate’s impact on weeds, the effects of climate change on agriculture, and the development of herbicide-resistant crops, focusing on Brazil as a case study. The history of transgenic crops, from glyphosate-resistant soybeans to newer technologies like dicamba and 2,4-D-resistance traits, is discussed, highlighting their impact on weed management.