To tailor the mechanical properties of rubber elastomers for technical applications they have to be usually reinforced by active fillers. Traditionally highly structured carbon blacks or precipitated silica serve this purpose. Recent developments in particle technology, biotechnology and chemical-thermal processes provide the availability of a variety of biobased functional fillers, i.e. micro- and nanocrystalline cellulose, lignin or hydro-thermal carbon, with well-defined particle properties. This makes an at least partial substitution of conventional reinforcing fillers in rubber compounds a perspective application. In our investigations we have studied a variety of bio-based fillers for their potential to reinforce and tailor the mechanical properties of rubbers.