A range of fully biobased unsaturated polyesters (bio-UPs) derived from 2,5-furandicarboxylic (FDCA), itaconic acid (IA), succinic acid (SA), and 1,3-propanediol (PD) were obtained via direct polycondensation. The chemical structures of the bio-UPs were identified by Fourier transfrom infrared spectroscopy and H-1 NMR before they were cured together with a biobased, nonvolatile reactive diluent, guaiacol methacrylate (GM). The thermal and mechanical characterizations of the cured bio-UPs were evaluated using thermogravimetric analysis, 3-point bending tests, and dynamic mechanical analysis. Results showed that the thermal properties, flexural strength, and modulus of the cured bio-UPs were greatly improved after the introduction of FDCA. The temperature of 5% thermal weight loss reached 330 degrees C, and the flexural strength and modulus reached 122.8 respectively. These results indicate that the bio-UPs have the potential to replace petroleum-based UPs.