He was born at Betsborough, Dunnahane, in the parish of Kilshanick, county Cork, on the 21st November, 1767.  His father was an officer in the British army, who had fought against the Irish Brigade in the memorable battle of Fontenoy, and who died in a high situation in the Royal Hospital at Kilmainham.  Thomas, the youngest of his three sons, was educated for the Protestant Church; but his inclinations sought a different field of action, and at the age of fifteen he left for India as a volunteer, where he served with his brother, Ambrose, whose gallantry in battle called down commendation from the English king.  Thomas Russell quitted India after five years’ service, and his return is ascribed to the disgust and indignation which filled him on witnessing the extortions, the cruelties, the usurpations, and brutalities, which were carried out and sanctioned by the government under which he served.  He left Ireland burdened with few fixed political principles and little knowledge of the world; he returned a full grown man, imbued with the opinions which he never afterwards abandoned.  He was then, we are told, a model of manly beauty, one of those favoured individuals whom we cannot pass in the street without being guilty of the rudeness of staring in the face while passing, and turning round to look at the receding figure.  Though more than six feet high, his majestic stature was scarcely observed, owing to the exquisite symmetry of his form.  Martial in his gait and demeanour, his appearance was not altogether that of a soldier.  His dark and steady eye, compressed lip, and some what haughty bearing, were occasionally strongly indicative of the camp; but in general the classic contour of his finely formed head, the expression of sweetness that characterised his smile, and the benevolence that beamed in his fine countenance, seemed to mark him out as one that was destined to be the ornament, grace, and blessing of private life.  His manners were those of the finished gentleman, combined with that native grace which nothing but superiority of intellect can give; he was naturally reserved and retiring in disposition, and his private life was distinguished by eminent purity and an unostentatious devotion to the precepts of religion.

Such was Thomas Russell when he made the acquaintance of Theobald Wolfe Tone in Dublin.  There is no doubt that the views and opinions of Tone made a profound impression on young Russell; it is equally certain, on the other hand, that Tone learned to love and esteem his new friend, whose sentiments were so much in accordance with his own.  Throughout Tone’s journal we find constant references to Thomas Russell, whom he always places with Thomas Addis Emmet at the head of his list of friends.  Early in 1791 Russell proceeded to Belfast to join the 64th Regiment, in which he had obtained a commission; before leaving Dublin he appears to have become a member of the Society of United Irishmen, and in Belfast he soon won the friendship and shared the councils of the patriotic men who were labouring for Ireland in that city.