Marcán
Marcán,  10th King of Uí Maine, died 556. Marcán was the first of two semi-historical kings who reigned subsequent to that of the first attested king of Uí Maine, Maine mac Cearbhall. Marcán appears to be unique among the dynasty in that he is not recorded in the genealogies, nor are there any families known to claim descent from him. Only one other king of Uí Maine, Marcán mac Tommáin (slain 653), bore his name, but their relationship is uncertain. References

 Annals of Ulster at CELT: Corpus of Electronic Texts at University College Cork
 Annals of Tigernach at CELT: Corpus of Electronic Texts at University College Cork
Revised edition of McCarthy's synchronisms at Trinity College Dublin. Byrne, Francis John (2001), Irish Kings and High-Kings, Dublin: Four Courts Press, 

Nobility from County Galway
Nobility from County Roscommon
6th-century Irish monarchs
Kings of Uí Maine