Groundwater is Canada’s largest source of freshwater and a critical yet underrepresented component of the national water system. More than one-third of Canadians rely on groundwater for drinking water, including approximately 80% of the rural population and over half of Indigenous communities. It supplies more than half of municipal drinking water in several provinces and territories and is the sole source in Prince Edward Island and the City of Guelph. Groundwater also underpins agriculture, energy production, and industry, and sustains rivers, lakes, wetlands, and ecosystems by contributing a substantial portion of annual streamflow, particularly during dry periods. Despite its importance, Canada remains the only G7 country without a nationally coordinated groundwater monitoring program. Federal freshwater monitoring focuses almost exclusively on surface water, while aquifer characterization at the national scale remains limited. Groundwater monitoring is instead carried out through a fragmented mix of provincial, territorial, municipal, Indigenous, academic, and private initiatives, constraining data consistency, accessibility, and national-scale assessment. Climate change, increasing water demand, and prolonged drought are already affecting groundwater levels in parts of Canada, with cascading impacts on surface water availability, ecosystems, and water security. Addressing these risks requires systematic, long-term monitoring of groundwater quantity and quality, particularly in areas of strong groundwater–surface water interaction. We argue for integrating groundwater into Canada’s freshwater monitoring architecture through a collaborative “network of networks,” with federal leadership in data integration, standardization, and aquifer characterization. Canada has the capacity to act; what is needed now is coordinated commitment.