We show experimentally that room-temperature ferromagnetism can be induced in ZnO/ZnS core/shell nanoparticles without any magnetic components. This ferromagnetism could be attributed to p-p coupling interactions between S 3p and O 2p electrons arising from the redistribution of charges between Zn and O or S atoms. Our present findings possibly open up a new way for introducing magnetism in semiconductor-based "spintronics" devices.