Abstarct: Advanced composite laminated cylindrical shells are used in various industries, including military industries and modern aerospace structures. The Study of the buckling and stress failure of these types of structures is of interest to many researchers around the world. In previous works, buckling and stress failure analyses of composite laminated cylindrical shells under mechanical loading were performed by researchers. In this thesis, thermal loading is also considered, so buckling and stress failure analyses of composite laminated cylindrical shells under mechanical or thermal loading is presented. In this research, linear buckling interacting curve method has been considered for buckling‐failure analysis and strength ratio baxsed on Tsai‐Wu failure criterion has been used for stress‐failure analysis. Also, the effects of dimensional changes, stacking sequences, and material properties on buckling and stress‐competitive failure are studied. The values obtained from this research are in good agreement with the results published in previous articles. In this thesis, composite cylindrical shells under mechanical or thermal loading are subjected to simultaneous stress and buckling failure analysis with analytical methods so that their failure load can be determined by considering both analyses.