OpenStreetMap (OSM) is a rich source of openly available volunteered geographic information. However, representations of geographic entities in OSM are highly diverse and incomplete. Recently emerged knowledge graphs (i.e. graph-based knowledge repositories) such as Wikidata, EventKG and DBpedia provide a rich source of contextual information about geographic entities and support semantic queries. Whereas knowledge graphs provide a wide range of complementary semantic information for geographic entities, highly useful for Web applications, identity links between OSM and knowledge graphs are still rare and are mainly manually defined by volunteers. The main goal of the WorldKG project is to facilitate world-scale interlinking of OSM datasets describing different geographic regions with knowledge graphs such as Wikidata, EventKG and DBpedia as well as completion of spatial knowledge in the knowledge graphs using OSM data.