The paper reviews the basic principles of friction stir welding, its methodology, and all other technical aspects. As reported by different researchers, the effect of varying welding variables such as tool geometry, tool-tilt angle and tool materials on the microstructure and mechanical properties of the welded materials, and weld quality are reported and discussed. The paper covers the various mechanical and metallurgical properties of similar/dissimilar aluminium alloys and other metal joints welded using friction stir welding (FSW). The attempt has been made to present a comprehensive review of some of the salient works carried out by various researchers pertaining to friction stir processing (FSP) /FSW of aluminium alloys. The paper also identifies the existing research gaps in the area of FSW, which should be explored in future.