Ceramic matrix composites (CMCs) reinforced with ceramic fibers have attracted significant interest due to their superior properties, including high-temperature resistance, excellent thermal shock resistance, and low density. These properties of interest enable their use in various strategic fields such as aerospace, automotive, energy, and Defense. However, the performance of CMCs is heavily dependent on the properties of the reinforcing fibers and several ongoing scientific and technological challenges related to their development have to be addressed. In this context, a partnership project has been formed between IRCER and CEA to develop a new generation of oxynitride fibers with specific electrical, mechanical, and thermal properties. In particular, the fiber reinforcement should have both thermochemical stability and thermomechanical resistance allowing it to operate at high temperatures for short periods of time. The fabrication process considered for developing such a fiber is the Polymer-Derived Ceramics (PDCs) route, which relies on the custom synthesis of pre-ceramic polymers that are subsequently converted into ceramic material after thermal treatment. By adjusting and fixing the molecular structure of the precursor in its polymeric state, this manufacturing method enables precise control over the composition and microstructure of the ceramic obtained after thermal treatment. The challenge lies in developing a preceramic polymer adapted for melt spinning process and leading to fibers showing the above-mentioned properties. Consequently, a key issue of this work is to highlight how chemistry, rheology, and structure are interrelated in the development of this new generation of oxynitrides Polymer-Derived Ceramic Fibers (PDCFs). This project is in line with the latest research and development programs conducted by IRCER and CEA to develop CMC components that address future societal challenges.