Synge suffered from Hodgkin's disease, a form of cancer at the time untreatable. He died just weeks short of his 38th birthday and was at the time trying to complete his last play, The Last Black Supper.
His grandfather, John Hatch Synge, was an admirer of the educationalist Johann Heinrich Pestalozzi and founded an experimental school on the family estate. His father, also called John Hatch Synge, was a barrister but contracted smallpox and died in 1872 at the age of 49. Synge's mother, who had a private income from lands in County Galway, moved the family to the house next door to her mother in Rathgar, Dublin. Synge, although often ill, had a happy childhood here, and developed an interest in ornithology along the banks of the River Dodder in the grounds of the nearby Rathfarnham Castle, and during family holidays at the seaside resort of Greystones, Wicklow, and the family estate at Glanmore.
Synge was educated privately at schools in Dublin and Bray, and later studied piano, flute, violin, music theory and counterpoint at the Royal Irish Academy of Music. He traveled to Europe to study music, but changed his mind and decided to focus on literature. He proved to be a talented student and won a scholarship in counterpoint in 1891. The family moved to the suburb of Kingstown (now Dún Laoghaire) in 1888, and Synge entered Trinity College, Dublin the following year, where he graduated with a BA in 1892. While at college, he studied Irish and Hebrew, as well as continuing his music studies and playing with the Academy orchestra in the Antient Concert Rooms.
During summer holidays with his family in Dublin, he met and fell in love with Cherrie Matheson, a friend of his cousin and a member of the Plymouth Brethren. He proposed to her in 1895 and again the next year, but she turned him down on both occasions because of their differing religious viewpoints. This rejection affected Synge greatly and reinforced his determination to spend as much time as possible outside Ireland.
In 1896 he visited Italy to study the language for a time before returning to Paris. Later that year he met William Butler Yeats, who encouraged Synge to live for a while in the Aran Islands and then return to Dublin and devote himself to creative work. That year he joined with Yeats, Lady Gregory, and George Russel to form the Irish National Theatre Society, which later would establish the Abbey Theatre. He also wrote an amount of literary criticism for Gonne's Irlande Libre and other journals as well as unpublished poems and prose in a decadent, fin de siècle style. These writings were eventually gathered together in the 1960s for his Collected Works. He also attended lectures at the Sorbonne by the noted Celtic scholar Henri d'Arbois de Jubainville.
Synge suffered his first attack of Hodgkin's disease in 1897 and also had an enlarged gland removed from his neck. The following year, he spent the summer on the Aran Islands. He spent the next five summers on the islands, collecting stories and folklore and perfecting his Irish, while continuing to live in Paris for most of the rest of the year. He also visited Brittany regularly. During this period, Synge wrote his first play, When the Moon has Set. He sent it to Lady Gregory for the Irish Literary Theatre in 1900, but she rejected it and the play was not published until it appeared in the Collected Works.
His first account of life on the islands was published in the New Ireland Review in 1898 and his book-length journal, The Aran Islands, was completed in 1901 and published in 1907 with illustrations by Jack Butler Yeats. Synge considered the work "my first serious piece of work". When Lady Gregory read the book's manuscript, she advised Synge to remove any direct naming of the place and adding more folk stories to it, but refused to because he wanted to create something more realistic. The book is a slow-paced reflection of life on the islands and reflects Synge's belief that beneath the Catholicism of the islanders it was possible to detect a substratum of the older pagan beliefs of their ancestors. His experiences on Aran were to form the basis for many of the plays of Irish peasant and fishing community life that Synge went on to write.
In 1903, Synge left Paris and moved to London. He had written two one-act plays, Riders to the Sea and The Shadow of the Glen the previous year. These met with Lady Gregory's approval and The Shadow of the Glen was performed at the Molesworth Hall in October 1903. Riders to the Sea was performed at the same venue in February the following year. The Shadow of the Glen, under the title In the Shadow of the Glen, formed part of the bill for the opening run of the Abbey Theatre from 27 December 1904 to 3 January 1905. Both plays were based on stories Synge had collected on the Aran Islands, and Synge relied on props from the Aran Islands to help set the stage. He also relied on Hiberno-English, the English dialect of Ireland, in order to reinforce its usefulness as a language; parts of this stemmed from his belief that Gaelic as a language could not survive.
The Shadow of the Glen was based on a story of an unfaithful wife and it was attacked in print by Irish nationalist leader Arthur Griffith as "a slur on Irish womanhood". Years later, Synge would write, "When I was writing The Shadow of the Glen some years ago, I got more aid than any learning could have given me from a chink in the floor of the old Wicklow house where I was staying, that let me hear what was being said by the servant girls in the kitchen. This encouraged more critical attacks that alleged that Synge described Irish women in an unfair manner. Riders to the Sea was also attacked by nationalists, this time Patrick Pearse, who decried it because of the author's attitude to God and religion. Furthermore, Synge's audience felt that he did a disservice to Irish nationalism for not idealizing his characters. However, later critics would attack Synge for idealizing the Irish peasantry too much. Despite these attacks, the plays are now part of the canon of English language theatre. A third one-act play, The Tinker’s Wedding was drafted around this time, but Synge initially made no attempt to have it performed, largely because of a scene where a priest is tied up in a sack, which, as he wrote to the publisher Elkin Mathews in 1905, would probably upset "a good many of our Dublin friends".
When the Abbey was set up, Synge was appointed literary advisor to the theatre and soon became one of the directors of the company, along with Yeats and Lady Gregory. However, he differed from Yeats and Lady Gregory in what he believed the Irish theatre should be, as he wrote to Stephen MacKenna:
I do not believe in the possibility of 'a purely fantastic, unmodern, ideal, breezy, spring-dayish, Cuchulainoid National Theatre'... no drama can grow out of anything other than the fundamental realities of life which are never fantastic, are neither modern nor unmodern and, as I see them, rarely spring-dayish, or breezy or Cuchulanoid.His next play, The Well of the Saints was staged at the theatre in 1905, again to nationalist disapproval, and again in 1906 at the Deutsches Theater in Berlin. The critic Joseph Holloway claimed the play combined "lyric and dirt".
The play widely regarded as Synge's masterpiece, The Playboy of the Western World, was first performed in the Abbey in January 1907. The comedy centers on the story of apparent parricide and attracted a wide hostile reaction from the Irish public. The Freeman's Journal described it as "an unmitigated, protracted libel upon Irish peasant men, and worse still upon Irish girlhood". Egged on by nationalists, including Arthur Griffith, who believed that the theatre was insufficiently politically active and described it as "a vile and inhuman story told in the foulest language we have ever listened to from a public platform", and with the pretext of a perceived slight on the virtue of Irish womanhood in the line "... a drift of chosen females, standing in their shift ..." At the time a shift was known as a symbol representing Kitty O'Shea and adultery. However, George Watson explained the real problem with the play when he says, "this heady mixture of English stereotypical images of Irish violence, of Irish resentment of those images, and of Synge's stress on violence, which for him is almost synonymous with vitality, is, far more than the word 'shift', what made The Playboy so explosive. A significant portion of the crowd rioted, causing the third act of the play to be acted out in dumb show.
Yeats returned from Scotland to address the crowd on the second night, and decided to call in the police. Press opinion soon turned against the rioters and the protests petered out. Yeats later referred to this incident in a speech to the Abbey audience in 1926 on the fourth night of Seán O'Casey's The Plough and the Stars, when he declared: "You have disgraced yourselves again. Is this to be an ever-recurring celebration of the arrival of Irish genius? Synge first and then O'Casey?
Although writing of The Tinker's Wedding begun at the same time as Riders to the Sea and The Shadow of the glen, it took Synge five years to complete, and was finished in 1907. It was not performed until 1909, and only then in London. The first critic to respond to the play was Daniel Corkery, who said, "One is sorry Synge ever wrote so poor a thing, and one fails to understand why it ever should have been staged anywhere. This claim was popularly held by critics for many decades after. That same year, Synge became engaged to the Abbey actress Maire O'Neill (formerly known as Molly Allgood). He died at the Elpis Nursing Home in Dublin. His Poems and Translations was published by the Cuala Press on 8 April with a preface by Yeats. Yeats and Molly Allgood completed Synge's unfinished final play, Deirdre of the Sorrows, and it was presented by the Abbey players in January 1910 with Allgood in the lead role. Synge died in Dublin, 24 March 1909.
Masefield felt that Synge's problems and thoughts about life originated with his poor health. In particular, Masefield claims that "His relish of the savagery made me feel that he was a dying man clutching at life, and clutching most wildly at violent life, as the sick man does". In stanza IV of Yeats's "In Memory of Major Robert Gregory", he summarizes his view that Synge was unhealthy, sick and in pain throughout his career:
The critic Vivian Mercier was amongst the first to recognise Samuel Beckett's debt to Synge. Beckett was a regular audience member at the Abbey in his youth and particularly admired the plays of Yeats, Synge and O'Casey. Mercier points out parallels between Synge's casts of tramps, beggars and peasants and many of the figures in Beckett's novels and dramatic works.
In recent years, Synge's cottage on the Aran Islands has been restored as a tourist attraction. An annual Synge Summer School has been held every summer since 1991 in the village of Rathdrum in Wicklow.