Abstract: Objective Due to the high risk of fatigue failure in welded joints of extruded aluminum alloy stiffened thin plates, it is necessary to study their fatigue strength to provide a basis for the fatigue assessment of actual high-speed craft structures. Methods Fatigue tests were conducted on welded joints of 5083-H116 aluminum alloy stiffened thin panels to obtain fatigue life data. The reliability of the test results was verified using the finite element method. Results Nominal stress and hot spot stress S-N curves for typical details were derived, providing S-N curves that more accurately reflected the fatigue test results. Conclusion The established S-N curves can serve as a reliable basis for the fatigue assessment of such welded joints and support the fatigue life prediction of practical high-speed craft structures.