A heavy-duty plug-in connector has a ground terminal that can be conveniently assembled and can comprise the greatest possible number of electrical crimp plug-in contacts (4,5). For this purpose, ground plug-in contacts (4′, 5′), likewise of a crimping configuration, are fitted in formations (13, 13′, 23, 23′) of the contact carriers (1, 2) for electrical contacting with metallic protective earthing elements (3, 3′, 3″, 3′″). For said contacting, the formations (13, 13′, 23, 23′) have a respective opening (130, 130′) or passage (230, 230′). In the formations (13, 13′, 23, 23′), not only ground plug-in contacts (4′, 5′) but also further plug-in contacts (4, 5) are arranged, so that the number of plug-in contacts (4, 5) of the plug-in connector is increased considerably.