This chapter analyzes the evolving relationship between the bioeconomy, agriculture, and the circular economy, drawing insights from the EU Horizon 2020 BioMonitor project. It begins by placing the bioeconomy within the broader sustainability agenda, revisiting classical economic thought, and demonstrating how principles of circularity can enhance the value of biological resources while respecting ecological limits. This chapter quantifies Europe’s bioeconomy’s size, growth trajectories, and material flows using newly developed indicators and methods such as environmentally extended input–output analysis, the Bio Flow Monitor, and the BioMAT model. It identifies sectoral hotspots and evaluates the socio-economic and environmental trade-offs involved. Case studies on sludge-based biofertilizer production and regional biorefineries illustrate how hybrid modeling captures the connections between upstream and downstream processes, employment effects, and uncertainties. The results indicate that the value added by bio-based sectors and job creation are growing, particularly in food production, biofuels, and high-value chemicals. However, these sectors still represent a modest share of total economic activity, and their benefits are contingent upon coherent policies, reliable data, and the cascading use of biomass. This chapter concludes by outlining future opportunities and challenges for a bioeconomy transition in the EU, including essential research, regulatory, and skills priorities needed.