Claude John Eyre Auchinleck was born in Aldershot on 21 June 1884. He was the eldest son of Colonel John Claude Alexander Auchinleck, Royal Horse Artillery and Mary Eleanor, daughter of John Eyre. Claude Auchinleck, like many of the senior officers in the British army in the Second World War, most notably, Field Marshals Harold Alexander, Alan Brooke, John Dill and Bernard Montgomery, was from an Anglo-Irish gentry background, though the family's origins were in the village of Auchinleck in Ayrshire. Given the number of Anglo-Irish officers who reached high rank in the British army, there is a tendency to see the Anglo-Irish officer as over-represented. H. J. Hanham noted that, ‘In terms of officers per head the Church of Ireland … was presumably the most army-orientated denomination in the British Isles.’ Correlli Barnett believed that the Anglo-Irish were a British version of the ‘Prussian Junker class’. However, Nick Perry's careful study of this issue suggests that the Anglo-Irish gentry were as likely to be commissioned into the army as Scots gentry (40 per cent of male gentry of military age), whereas the English and Welsh figure stood at 30 per cent.

Claude Auchinleck himself, when relinquishing the colonelcy of the Royal Inniskilling Fusiliers, which he held between 1941 and 1947, identified his Irish origins by stating, ‘My forefathers lived in Enniskillen and Fermanagh for very many years and this makes me all the prouder to have belonged to the regiment.’ In fact Auchinleck's father had equally firm roots in Counties Tyrone and Wexford and his mother's family came from Galway. Auchinleck's ‘Irishness’ can be questioned by the fact that the Irish Times, which had been the newspaper of the Anglo-Irish establishment, though it had moved far away from these origins by 1981, did not carry a full length obituary of him and the recently published Dictionary of Irish Biography does not devote an entry to him. T. G. Fraser's overstates the contrary interpretation by noting that, ‘Two things stand out from Auchinleck's background and early life: his sense of identity as an Ulsterman and his commitment to India.’