The first virtual cranial endocast of a lungfish from the Early Devonian, Dipnorhynchus sussmilchi , is described. Dipnorhynchus, only the fourth Devonian lungfish for which a near complete cranial endocast is known, is a key taxon for clarifying primitive character states within the group. A ventrally-expanded telencephalic cavity is present in the endocast of Dipnorhynchus demonstrating that this is the primitive state for “true” Dipnoi. Dipnorhynchus also possesses a utricular recess differentiated from the sacculolagenar pouch like that seen in stratigraphically younger lungfish ( Dipterus, Chirodipterus, Rhinodipterus ), but absent from the dipnomorph Youngolepis . We do not find separate pineal and para-pineal canals in contrast to a reconstruction from previous authors. We conduct the first phylogenetic analysis of Dipnoi based purely on endocast characters, which supports a basal placement of Dipnorhynchus within the dipnoan stem group, in agreement with recent analyses. Our analysis demonstrates the value of endocast characters for inferring phylogenetic relationships.