A friend of the family, Rev. Nathaniel Boyse, arranged to have Curran educated at Midleton, County Cork. He studied law at Trinity College, Dublin (he was described as "the wildest, wittiest, dreamiest student") and continued his legal studies at King's Inns and the Middle Temple. He was called to the Irish bar in 1775. Upon his first trial, his nerves got the better of him and he couldn't proceed. His short stature, boyish features, shrill voice and a speech impediment hindered his career, and earned him the nickname "Stuttering Jack Curran".

However, he could speak passionately in court on subjects close to his heart. He eventually overcame his nerves, and got rid of his speech impediment by constantly reciting Shakespeare and Bolingbroke in front of a mirror, and became a noted orator and wit. His speeches were emotional, rather than rational.

His occasional tendency of challenging people to duels (he fought five in all) rather than compromise his values, along with his skilful oratory, quick wit and his championing of popular Irish causes such as Catholic Emancipation and the enlargement of the franchise, made him one of the most popular lawyers in Ireland. He also could speak Irish, still the language of the majority at that time. He wrote a large amount of humorous and romantic poetry.

The case which cemented Curran's popularity was that of Father Neale and Lord Doneraile at the County Cork Assizes in 1780. Father Neale, an elderly Catholic priest in County Cork, criticised an adulterous parishioner. The adulterer's sister was mistress to Lord Doneraile, a cruel Protestant landlord. Doneraile demanded that Neale recant his criticism of his mistress' brother. When the priest stood by his principles, Doneraile horse-whipped him, secure in the confidence that a jury of the time would not convict a Protestant on charges brought forward by a Catholic. Curran, who had a passion for lost causes, represented the priest and won over the jury by setting aside the issue of religion. The jury awarded Curran's client 30 guinea. Doneraile challenged Curran to a duel, in which Doneraile fired and missed. Curran declined to fire.

His Catholic sympathies earned him the nickname The Little Jesuit of St. Omers. His drinking club The Order of St. Patrick also included Catholic members along with liberal lawyers who then had to be Protestant. The Club members were called The Monks of the Screw, as they appreciated wine and corkscrews. Curran was its Prior and consequently named his Rathfarnham home "The Priory".

A liberal Protestant whose politics were similar to Henry Grattan, he employed all his eloquence to oppose the illiberal policy of the Government, and also the Union with Britain. Curran stood as Member of Parliament (MP) for Kilbeggan in 1783. He subsequently represented Rathcormack between 1790 and 1798 and served then for Banagher from 1800 until the Act of Union in 1801, which bitterly disappointed him; he even contemplated emigrating to the United States. He also visited France in the 1780s and in 1802, and considered that an Ireland ruled by the United Irishmen under French protection would be as bad as, if not worse than, British rule.

However, he defended several of the United Irishmen in prominent high treason cases in the 1790s. Among them were the Revd. William Jackson, Archibald Hamilton Rowan, Wolfe Tone, Napper Tandy, The Sheares Brothers, Lord Edward Fitzgerald, William Orr and William Drennan. His main argument in defence was that the government often used one witness to secure a high treason case, while in England the prosecution had to use two or more. Consequently success depended on his lengthy examination of a single witness to try to find an inconsistency.

He was appointed Master of the Rolls in Ireland in 1806, following Pitt's replacement by a more liberal cabinet. He retired in 1814 and spent his last three years in London. He died in his home in Brompton in 1817. In 1837, his remains were transferred from Paddington Cemetery, London to Glasnevin Cemetery, where they were laid in an 8-foot-high classical-style sarcophagus.

He married in 1774, to his cousin Sarah Creagh (1755—1844), the daughter of Richard Creagh, a County Cork physician. His eldest daughter Amelia was born in 1775, and eight more children resulted from the union, but his marriage disintegrated, his wife eventually deserting him and eloping with Reverend Abraham Sandys, whom Curran sued afterwards in 1795.

His daughter Sarah's brief romance with the rebel Robert Emmet, who was hanged for treason in 1803, scandalised Curran, who had tried to split them up at one point. He was arrested and agreed to pass their correspondence on to the attorney general. In the circumstances he could not defend Emmet. He was suspected with involvement in Emmet's Rebellion, but was completely exonerated. However, his friend Lord Kilwarden was killed by the rebels, and he lost any faith in the beliefs of the United Irishmen.

• "I have never yet heard of a murderer who was not afraid of a ghost."

• "Assassinate me you may; intimidate me you cannot."

• "His smile is like the silver plate on a coffin."

• "In this administration, a place can be found for every bad man."

• "Twenty four millions of people have burst their chains, and on the altar erected by despotism for public slavery, have enthroned the image of public liberty" - Speaking of the French Revolution, 4 February 1790.

• "It is the common fate of the indolent to see their rights become a prey to the active. The condition upon which God hath given liberty to man is eternal vigilance; which condition if he break, servitude is at once the consequence of his crime and the punishment of his guilt." -- John Philpot Curran: Speech upon the Right of Election for Lord Mayor of Dublin, 1790. (Speeches. Dublin, 1808.) as quoted in Bartlett's Familiar Quotations

• "No matter with what solemnities he may have been devoted on the altar of slavery, the moment he touches the sacred soil of Britain, the altar and the god sink together in the dust; his soul walks abroad in her own majesty; his body swells beyond the measure of his chains which burst from around him, and he stands redeemed, regenerated, and disenthralled, by the irresistible genius of universal emancipation." - (Curran's speech in defense of James Somersett, a Jamaican slave who declared his freedom upon being brought to Britain [where slavery was banned] by his master; quoted extensively by U.S. abolitionists such as Harriet Beecher Stowe in Uncle Tom's Cabin, Chapter 37. Frederick Douglass always recited this speech on stage when playing Curran.)

• "Evil prospers when good men do nothing." (Also attributed to Edmund Burke; the quote cannot be definitely traced to either man.)

• Judge: (to Curran, whose wig was awry) Curran, do you see anything ridiculous in this wig?

Curran: Nothing but the head, my lord!

• "My dear doctor, I am surprised to hear you say that I am coughing very badly, as I have been practising all night."

• "When I can't talk sense, I talk metaphor."

• "Everything I see disgusts and depresses me: I look back at the streaming of blood for so many years, and everything everywhere relapsed into its former degradation - France rechained, Spain again saddled for the priests, and Ireland, like a bastinadoed elephant, kneeling to receive the paltry rider." - Written in a letter, after the exile of Napoleon Bonaparte.

• "If sadly thinking, with spirits sinking,

Could more than drinking my cares compose,

A cure for sorrow my sighs would borrow

And hope tomorrow would end my woes.

But as in wailing there's naught availing

And Death unfailing will strike the blow

And for that reason, and for a season,

Let us be merry before we go.

To joy a stranger, a wayworn ranger,

In every danger my course of I've run

Now hope all ending, and death befriending,

His last aid lending, my cares are done.

No more a rover, or hapless lover,

My griefs are over -- my glass runs low;

Then for that reason, and for a season,

Let us be merry before we go." - ("The Deserter's Meditation")

• "O Erin how sweetly thy green bosom rises,

An emerald set in the ring of the sea,

Each blade of thy meadows my faithful heart prizes,

Thou queen of the west, the world's cushla ma chree."

One night, Curran was dining with Justice Toler, a notorious "hanging judge".

Toler: Curran, is that hung-beef?

Curran: Do try it, my lord, then it is sure to be!

A wealthy tobacconist, Lundy Foot, asked Curran to suggest a Latin motto for his coach. "I have just hit on it!', exclaimed Curran. "It is only two words, and it will explain your profession, your elevation, and your contempt for the people's ridicule; it has the advantage of being in two languages, Latin and English, just as the reader chooses. Put up "Quid Rides" upon your carriage!" (A quid was a lump of tobacco to be chewed; in Latin "Quid rides" means: "so you may laugh").

Curran hated the Act of Union, which abolished the Parliament of Ireland and amalgamated it with that of Great Britain. The parliament had been housed in a splendid building in College Green, Dublin, which faced an uncertain future. "Curran, what do they mean to do with this useless building? For my part, I hate the very sight of it!" said one lord, who was for the Act of Union. "I do not wonder at it, my lord", said Curran contemptuously. "I have never yet heard of a murderer who is not afraid of a ghost."

Curran arrived at court late one morning. The judge, Viscount Avonmore, demanded an explanation. "On my way to court, I passed through the market...""Yes, I know, the Castle Market," interrupted Lord Avonmore."Exactly, the Castle Market, and passing near one of the stalls, I beheld a brawny butcher brandishing a sharp gleaming knife. A calf he was about to slay was standing, awaiting the deathstroke, when at that moment...that critical moment...a lovely little girl came bounding along in all her sportive mirth from her father's stall. Before a moment had passed the butcher had plunged his knife into the breast of...""Good God! His child!" sobbed the judge, deeply affected. Curran carried on:"No, the calf, but your Lordship often anticipates."

A prosecutor, infuriated by Curran's insults, threaten to put him in his pocket. "If you do that," replied Curran, "you will have more law in your pocket than you ever had in your head."

In debate with John Fitzgibbon, 1st Earl of Clare, Fitzgibbon rebutted one of Curran's arguments by saying "If that be the law, Mr. Curran, I shall burn all my law books." To which he replied "You had better read them first, my lord."

Lord Byron said, after the death of Curran, "I have heard that man speak more poetry than I have seen written", and, in a letter to Thomas Moore, 1 October 1821, "I feel, as your poor Curran said, before his death, 'a mountain of lead upon my heart, which I believe to be constitutional, and that nothing will remove it but the same remedy.'".

Karl Marx recommended to Engels that he read the speeches of John Philpot Curran in a letter of 10 December 1869: **"You must get Curran's Speeches edited by Davies (sic) Davis (London: James Duffy, 22, Paternoster Row). .... I consider Curran the only great lawyer (people's advocate) of the eighteenth century and the noblest personality, while Grattan was a parliamentary rogue, but because you will find quoted there all the sources for the United Irishmen. "