Abstract: A method for manufacturing a large-sized seamless dome, comprises providing a semi-finished product and hot forging by upsetting the semi-finished product to form a blank with a developed surface greater than that of the semi-finished product and less than the developed surface of the wall of the dome. The blank is hot formed to create a preform having a developed surface less than or equal to the developed surface of the wall. The preform comprises at least two consecutive portions extending radially in the continuation of one another away from the central axis, such that for all the portions, the average thicknesses and/or convexities of two consecutive portions are distinct. The preform undergoes hot deformation under a press between a die and a punch to form the wall.