The military and theatrical worlds of the First French Empire were a revelation to Beyle. He travelled extensively in Germany and was part of Napoleon's army in the 1812 invasion of Russia), but formed a particular attachment to Italy, where he spent much of the remainder of his career, serving as French consul at Trieste and Civitavecchia and writing. His novel The Charterhouse of Parma, among other works, is set in Italy, which he considered a more sincere and passionate country than Restoration France. An aside in that novel, referring to a character who contemplates suicide after being jilted, speaks volumes about his attitude towards his home country: "To make this course of action clear to my French readers, I must explain that in Italy, a country very far away from us, people are still driven to despair by love."

Beyle used the pseudonym "Stendhal", supposedly chosen as an anagram of "Shetland" (although Georges Perec may have invented this explanation - references to Le Rouge et le Noir (The Red and the Black) feature extensively in Perec's unfinished last novel 53 jours). Alternatively, some scholars believe he borrowed his nom de plume from the German city of Stendal as a homage for Johann Joachim Winckelmann.

Stendhal was a dandy and wit about town in Paris, as well as an inveterate skirt-chaser. His genuine empathy towards women is evident in his books (Simone de Beauvoir spoke highly of him in The Second Sex), and contrasts with his obsession with sexual conquests. He seems to have preferred the desire to the consummation. One of his early works is On Love, a rational analysis of romantic passion. This fusion, or tension, of clearheaded analysis with romantic feeling is typical of Stendhal's great novels; he could be considered a Romantic realist.

Contemporary readers did not fully appreciate Stendhal's realistic style during the Romantic period in which he lived; he was not fully appreciated until the beginning of the 20th century. He dedicated his writing to "the Happy Few", referring to those who would one day recognise his own genius. Today, Stendhal's works attract attention for their irony and psychological and historical aspects.

Stendhal was an avid fan of music, particularly the composers Cimarosa, Mozart, and Rossini, the latter of whom he wrote an extensive biography, Vie de Rossini (1824), now more valued for its wide-ranging musical criticism than for its historical accuracy.

He died in Paris in 1842 and is interred in the Cimetière de Montmartre.

Stendhal's brief, saucy memoir, Souvenirs d'Egotisme (Memoirs of an Egotist) was published posthumously in 1892. Also published was a more extended autobiographical work, thinly disguised at the Life of Henry Brulard.