A connector for devices intended to collect and dispense liquid solutions for pharmaceutical and/or nutritional use is described. The connector comprises a closing plug pierceable by pressing a needleless introduction/collection tang. The closing plug comprises a check valve with closing lips openable by introducing said tang and elastically reclosable after extracting the introduced tang and further comprising a pierceable and elastically sealingly reclosable membrane placed to hermetically close the inlet end of said check valve. Said closing lips are located at one end of an elastically deformable plastic material body, which is longitudinally crossed by a thin rectangular section slot, the slot being closed on the other end by said pierceable and elastically reclosable membrane.