The past 50 years have seen the emergence of biomonitoring as an essential means of generating the knowledge needed to inform protection and restoration of freshwater ecosystems around the world. Yet, despite the successes of freshwater biomonitoring, most freshwater ecosystems remain unmonitored and degradation of freshwaters continues at a rapid rate with new threats and novel stressors emerging. Many of these stressors are difficult to assess using existing techniques and application of new approaches has been slow. Clearly, freshwater biomonitoring faces many important challenges that must be addressed to ensure that freshwaters are effectively managed in the coming decades. Our goal was to identify the Grand Challenges facing freshwater biomonitoring and thereby initiate research and practice that can address these challenges. We polled more than 200 biomonitoring practitioners from around the globe as to what they considered to be the most important challenges. From their submissions we identified five Grand Challenges and 18 associated sub-challenges. Grand Challenges to biomonitoring were to (1) develop protocols; (2) construct infrastructure; (3) expand ecological context; (4) empower communities; and (5) ensure FAIR data. For each challenge we outline the current state of biomonitoring practice and provide initial ideas of promising future pathways and approaches to addressing these Grand Challenges. By identifying and describing these challenges, we better position freshwater biomonitoring to take advantage of emerging opportunities and promote its capacity to meet current needs and those that will arise in the coming decades.