There is a continuing trend in the industry to use parts made from a combination of different materials. These components can be joined in a variety of ways, but the main joining process for aluminium alloys is welding. However, one of the problems of welding is still the selection of the appropriate welding parameters to achieve the desired weld quality. In this thesis, the welding of aluminium alloy 5083-O by FSW was designed and analysed. Welded joints were produced where the welding speed was varied from 190 mm/min to 380 mm/min, at a constant tool rotation speed. First, the welded joints were evaluated visually and weld samples were prepared for tensile testing. The mechanical properties were measured by tensile testing and the fracture surface of the welded joint was analysed. Then macro contours were made, microstructure analysis was carried out and the gap filling of the two weld designs was compared. The variation of the welding speed had a minimal effect on the mechanical properties, which was observed in the lower tensile strength of the welded joint welded with higher heat input. The average tensile strength of the welded joints is less than 10% lower than the base material and the elongation is reduced by 1 to 2%. Filling of the weld joint showed good, repeatable results for both weld designs. The observed microstructure did not differ between the different welding speeds.