These files contain data supporting all results reported in Dreiling, R. J. et al. Degradable Thermosets via Orthogonal Polymerizations of a Single Monomer. In Dreiling, R. J. et al we found: Crosslinked thermosets are highly durable materials, but overcoming their petrochemical origins and inability to be recycled poses a grand challenge. Many strategies to access crosslinked polymers that are bioderived or degradable-by-design have been proposed, but they require multiple resource intensive synthesis and purification steps and are not yet feasible alternatives to conventional consumer materials. Here, we present a modular, one-pot synthesis of degradable thermosets from the commercially available, biosourced monomer 2,3-dihydrofuran (DHF). In the presence of a Ru catalyst and photoacid generator, DHF undergoes slow ring-opening metathesis polymerization to give a soft polymer; then, exposure to light triggers strong acid generation and promotes the cationic polymerization of the same DHF monomer to spatially crosslink and strengthen the material. By manipulating catalyst loading and light exposure, we can access materials with physical properties spanning orders of magnitude and achieve spatially resolved material domains. Importantly, the DHF-based thermosets undergo stimuli-selective degradation and can be recycled to monomer under mild heating. The use of two distinct polymerization mechanisms on a single functional group allows the synthesis of degradable and recyclable thermoset materials with precisely controlled properties.