The complexity of natural ecosystems makes the study of ecology in the field an immense challenge. These complexities often hinder field studies from uncovering the mechanisms driving key ecological processes, such as biodiversity maintenance, community assembly, ecosystem function and service provision, and ecological stability. In viewing ecology through the lens of complex systems science, this symposium advocates for an approach that combines theory, experimentation, and field observations to better understand the natural world. We present a wide range of studies focusing on complementary issues in complex ecological systems such as how to understand the mechanisms listed above. We highlight how complexity in ecology can be both a challenge and an opportunity, showcasing its relevance across various levels of ecological organization, scales, and emerging research questions. By bringing together experts in theoretical and empirical ecology, we aim to address contemporary ecological challenges. This symposium emphasizes the need to recognize ecology as a complex system science to make progress in understanding the fundamental mechanisms driving ecological processes upon which human well-being depends.