Austria and the Alps are particularly affected by global warming. Compared to the global average, the temperature increase is twice as high and was in 2022 already +2.3 °C above pre-industrial levels. Specific actions to achieve national and international climate goals include the massive expansion of renewable energy sources and the decarbonization of the mobility sector. As part of the flagship project HyFleet - Decarbonization of Mobility by Hydrogen Powered Special Vehicle Fleets, an innovative overall solution for the operation of emission-free special purpose vehicles in the Alpine region is being demonstrated. For this purpose, a hydrogen-powered fuel cell powertrain for the universally usable side-by-side vehicle class is being developed and tested under real conditions in the hiking region Hinterstoder-Wurzeralm. The scope of this master thesis is the design of the required fuel cell system, consisting of a fuel cell stack and auxiliary units. The aim of this work is to integrate a fuel cell powertrain into a prototype side-by-side vehicle. The integration of the fuel cell components into the existing vehicle is based on a comprehensive packaging analysis with focus on functionality and system efficiency. In the first step, a requirements analysis is carried out and the goals for the vehicle in general and for the subsystems are summarized in the requirement and target specifications. The available space in the prototype vehicle for the system integration is identified and the components are analyzed in terms of dimensions, volume and weight. During the packaging process, the technically feasible positions for the components are determined and three packaging solutions for the fuel cell system are designed. The design process is in accordance with the V-model and the VDI 2221 and uses PTC Creo, a 3D CAD software. The different packaging solutions are evaluated in a utility analysis based on center of gravity, piping lengths, component accessibility and integrity of the existing vehicle frame. The best result is achieved with package solution three, which does not require any changes to the vehicle chassis. The final design of the individual subsystems (cathode subsystem, thermal management and hydrogen storage system) is realized based on the selected package solution. An innovative and compact design of the subsystems developed in this thesis results in the feasible integration of the fuel cell system into the existing vehicle chassis. The findings provide a basis for the series production of hydrogen-powered special purpose vehicles.