Using the by-product biopolymer lignin and nanoparticles of magnetite, well-known for its nontoxicity and magnetic properties, novel nanomagnetite-lignin hybrid materials were synthesized. In the first step, magnetite was produced via a co-precipitation method with hydrothermal treatment, and was found to have a particle size of around 20 nm. Nano-Fe3O4 was then combined with pre-activated lignin to obtain hybrids with various magnetite-lignin ratios, whose physicochemical and magnetic properties were thoroughly analyzed. Thermal analysis showed the hybrids to have higher thermal stability than pure lignin. Based on Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy it was demonstrated that the Fe3O4 and lignin are connected via Fe-O-C bonds. Further measurements showed the nanomagnetite-lignin hybrid materials to have good magnetic properties. The results of this study suggest that the synthesized hybrids may find practical applications in many fields of science and industry. (C) 2017 Elsevier B.V. All rights reserved.