Metal-organic frameworks (MOFs) have emerged as a new class of ionic conductors because of their tuneable and highly ordered microporous structures. The ionic conduction of various ionic carriers, such as a proton (H+), hydroxide ion (OH-), lithium ion (Li+), sodium ion (Na+), and magnesium ion (Mg2+), in the pores of MOFs has been widely investigated over the past decade. Reports reveal that the porous or channel structures of MOFs are fundamentally suitable as ion-conducting pathways. There are clear differences in the basic designs of ion-conductive MOFs, i.e., the introduction of ionic carriers and construction of efficient ion-conducting pathways, depending on the ionic carriers. We summarize the examples and fundamental design of highly ion-conductive MOFs with various types of ionic carriers.