Seosamh Mac Grianna(1900-1990) - or, as he was known in his Gaeltacht, Joe Fheilimí Dhónaill Phroinsiais - is the great Irish language writer of Ulster in the twentieth century. Born in the turn of the century in Donegal, he was an outsider from the start. Together with his brothers, he took part in the Irish independence and civil wars in the beginning of the twenties; after a spell in prison with other Irish Republicans, he worked as a translator of classical English literature for the state publishing house, An Gúm. Among his most important translations are Joseph Conrad's Almayer's Folly (in Irish, Díth céille Almayer) as well as the novels by his fellow prisoner and fellow Republican Peadar O'Donnell, Adrigoole (Eadarbhaile) and The Islanders (Muintir an Oileáin).

He was a very promising author, but was treated in a shameful way by An Gúm - for example, his novel An Druma Mór could only be published in the 1960s, although written and submitted for publication thirty years earlier. This novel is a great allegory about the change of Irish society in the twentieth century, where the drama develops around a big drum - the symbol of the community spirit in a small village - and the two parties each trying to seize the drum.

His subsequent works included Mo Bhealach Féin, an introspective account of his wanderings as a tramp in Ireland and Wales, and the novel fragment Dá mBíodh Ruball ar an Éan - "If the Bird had a Tail". This book he could never complete, as he suffered a depressive psychosis which cut short his literary career, in 1935. Mo Bhealach Féin indicates such a development much stronger than the novel fragment, which is both funny and witty.

Seosamh died at a very advanced age, in 1990. Although he never resumed his career, he spent the end of his life liked and admired by young Irish language writers from Northern Ireland, such as Pól Ó Muirí and Séamus Mac Annaidh.