Strehler was born in Barcola, Trieste; He became suddenly fatherless at the age of three, his grandfather, Olimpio Lovrich, becoming his father figure. Olimpio was one of the finest horn players of his day and the impresario of the Teatro Comunale Giuseppe Verdi, Trieste's Opera House. When he was seven, his grandfather died and he moved to Milan with his mother and grandmother.
As a child, Giorgio was not impressed by theater. He found it "false" and decided it did not have the power to stir one's emotions as film did. His opinions changed one hot summer night while on his way to the cinema. He noticed a sign advertising the Air-Conditioning posted by the Odeon theater. He walked in for some relief from the weather to see a performance of Carlo Goldoni's Una delle ultime sere di Carnevale being given by a company from Venice. He went every evening for the next few days to see more plays by Goldoni. Newly inspired by the theater, he applied and was accepted to the theater school Accademia dei Filodrammatici.
During the war he went into exile in Switzerland. With Geneva's Compagnie des Masques he directed the world premiere of Albert Camus’ Caligula. After the war he became a theater critic for Milano Sera but he preferred making theater rather than writing about it. It was at this time that he started the Piccolo Teatro di Milano with Paolo Grassi. It opened on 17 May 1947 in the auditorium of the Broletto cinema with Maxim Gorky's The Lower Depths. Few days later they gave Carlo Goldoni's long forgotten Arlecchino: Servant of Two Masters commedia dell'arte, which would go on to become the longest running play in Italian theater. In that same year he also directed La traviata at La Scala, the first of many opera productions he would direct.
Giorgio Strehler focused on theater which was culturally relevant. He did not want to "pay an abstract homage to culture" or "to offer a mere distraction... passive contemplation". Instead both Giorgio and Paolo agreed that theater was "a place where people gather to hear statements that they can accept or reject".
In the 1950s he directed several plays by Bertolt Brecht with whom he would become close friends sharing his political beliefs. In 1956 Brecht attended a production of his Threepenny Opera. Back in Berlin he wrote "... thank you for the excellent performance of my Threepenny Opera which you have realized with a great director. Fire and freshness, ease and precision distinguish this performance from many others I have seen... it would be a joy and an honor for me if your theater could perform... at the Berliner Ensemble's Theater... which witnessed the first performance of this work".
His love for William Shakespeare (Coriolanus, The Tempest, King Lear, Twelfth Night, Macbeth), Luigi Pirandello (Enrico IV), and Anton Chekhov (The Cherry Orchard, Platonov) was unmistakable; but he always returned to Goldoni repeating the same plays decades later.
He created the role of theater director (regista was actually coined in 1929) in Italy all by himself. Until he came plays were for the most part still put on by traveling companies that were a microcosm unto themselves. They directed themselves. They had never heard of a director. He also gave prominence to Italian authors, though few in number. Strehler used to say that "Italian theater has produced few important dramatic authors - Niccolò Machiavelli, Carlo Goldoni, Luigi Pirandello - but an enormous number of actors. Between 1500 and 1700, every self-respecting court in Europe had to have a company of Italian actors".
He originally had not intended to become an actor. He enrolled in fact in the law school at the University of Milan planning to become a criminal lawyer. He said "a profession as I imagined it was very close to the theater". But then war came and it changed everything.
He has influenced three generations of actors and inspired many around the world. His influence in the English speaking world is less felt since he spoke little English and did not direct many plays in this language. However he was given the Légion d'honneur by the French government and was named director of the "Union of the Theatres of Europe" in Paris in 1985. The first Pan-European theater project. He was President of the jury at the Cannes Film Festival in 1982. In 1990 he was the recipient of the Europe Theatre Prize.
The visual impact of his productions always concerned Strehler. The stage designers Luciano Damiani and later Ezio Frigerio closely collaborated with Strehler for many years, both for theatrical and operatic productions.
On October 10, 2005, a stretch of road in front of the Politeama Rossetti in Trieste was dedicated to Giorgio Strehler.