A gas burner for a domestic cooktop of the type having a burner cup suitable to be fixed to the cooktop and provided with at least part of the structure for at least one primary-air gas mixer, a burner body that may be joined to the burner cup, the burner body having at least part of the structure for at least one primary air-gas mixture delivery chamber, and a burner cover that may be joined to the burner body to complete the at least one primary-air gas mixture delivery chamber, as web as at least one flame-spreader that is made in one piece with the burner cover. Advantageously, the burner cover and the at least one flame-spreader are made of a steel, or iron, or iron-alloy sheet.