Abstract: A protective helmet with a dome having a bottom edge. A chin-strap system comprises a rigid right arm and a rigid left arm. Each has an attachment portion fastened to a respective side of the dome and a substantially horizontal portion projecting forwardly from the attachment portion. A reception space is formed between the bottom edge of the dome and an arm for receiving an ear of the user of the protective helmet. The reception space is open towards the front and is defined, towards the back and downwardly, by the arm under consideration and upwardly by the bottom edge of the dome. A flexible strip is fastened between the two front ends of the arms.