Baudelaire was born in Paris, France in 1821. His father, François Baudelaire, a senior civil servant and amateur artist, was thirty-four years older than Baudelaire's mother Caroline. François died during Baudelaire's childhood, in 1827. The following year, Caroline married Lieutenant Colonel Jacques Aupick, who later became a French ambassador to various noble courts. Baudelaire's relationship with his mother was a close and complex one, and it dominated his life. He later stated "I loved my mother for her elegance. I was a precocious dandy"; and in a letter to her that, "There was in my childhood a period of passionate love for you". Aupick, a rigid disciplinarian, though concerned for Baudelaire's upbringing and future, soon came to be at odds with his stepson's artistic temperament. Baudelaire was educated in Lyon, where he was forced to board away from his mother (even during holidays) and accept his stepfather's rigid methods, which included depriving him of visits home when his grades slipped. Later, he attended the Lycée Louis-le-Grand in Paris. Baudelaire was erratic in his studies, at times diligent, at other times prone to "idleness". Upon gaining his degree in 1839, he was undecided about his future. His stepfather had in mind a career in law or diplomacy, but instead Baudelaire decided to embark upon a literary career, and for the next two years led an irregular life, socializing with other bohemianartists and writers.

Baudelaire began to frequent prostitutes and may have contracted gonorrhea and syphilis during this period. He went to a pharmacist known for venereal disease treatments, on recommendation of his older brother Alphonse, a magistrate. For a while, he took on a prostitute named Sara as his mistress and lived with his brother when his funds were low. His stepfather kept him on a tight allowance which he spent as quickly as he received it. Baudelaire began to run up debts, mostly for clothes. His stepfather demanded an accounting and wrote to Alphonse: "The moment has come when something must be done to save your brother from absolute perdition." In the hope of reforming him and making a man of him, his stepfather sent him on a voyage to Calcutta, India in 1841, under the care of a former naval captain. Baudelaire's mother was distressed both by his poor behavior and by the proposed solution.

The arduous trip, however, did nothing to turn Baudelaire's mind away from a literary career or from his casual attitude toward life, so the naval captain agreed to let Baudelaire return home. Though Baudelaire later exaggerated his aborted trip to create a legend about his youthful travels and experiences, including "riding on elephants," the trip did provide strong impressions of the sea, sailing, and exotic ports, that he later employed in his poetry. Baudelaire returned to Paris after less than a year's absence. Much to his parents' chagrin, he was more determined than ever to continue with his literary career. Soon, Baudelaire returned to the taverns to philosophize, recite his unpublished poems and enjoy the adulation of his artistic peers. At twenty-one, he received a good-sized inheritance of over 100,000 francs, plus four parcels of land, but squandered much of it within a few years, including borrowing heavily against his mortgages. He quickly piled up debts far exceeding his annual income and, out of desperation, his family obtained a decree to place his property in trust. During this time he met Jeanne Duval, the illegitimate daughter of a prostitute from Nantes, who was to become his longest romantic association. She had been the mistress of the caricaturist and photographer Nadar. His mother thought Duval a "Black Venus" who "tortured him in every way" and drained him of money at every opportunity.

While still unpublished in 1843, Baudelaire became known in artistic circles as a dandy and free-spender, buying up books, art and antiques he couldn't afford. By 1844, he was eating on credit and half his inheritance was gone. Baudelaire regularly implored his mother for money while he tried to advance his career. He met Balzac around this time and began to write many of the poems which would appear in Les fleurs du mal. His first published work was his art review "Salon of 1845," which attracted immediate attention for its boldness. Many of his critical opinions were novel in their time, including his championing of Delacroix, but have since been generally accepted. Baudelaire proved himself to be a well-informed and passionate critic and he gained the attention of the greater art community. That summer, however, despondent about his meager income, rising debts, loneliness and doubtful future, because "the fatigue of falling asleep and the fatigue of waking are unbearable," he decided to commit suicide and leave the remainder of his inheritance to his mistress. However, he lost his resolve and wounded himself with a knife only superficially. He implored his mother to visit him as he recovered but she ignored his pleas, perhaps under orders from her husband. For a time, Baudelaire was homeless and completely estranged from his parents, until they relented due to his poor condition.

In 1846, Baudelaire wrote his second Salon review, gaining additional credibility as an advocate and critic of Romanticism. His support of Delacroix as the foremost Romantic artist gained widespread notice. The following year Baudelaire's novella La Fanfarlo was published.

Baudelaire took part in the Revolutions of 1848. For some years, he was interested in republican politics; but his political tendencies were more emotional positions than steadfast convictions, and spanned Blanquism, sympathy with the ideas of Histoire de la Raison d'Ėtat of Giuseppe Ferrari, as well as with the ultramontane critique of liberalism of Joseph de Maistre. His stepfather, also caught up in the Revolution, survived the mob and was appointed envoy extraordinary to Turkey by the new government despite his ties to the deposed royal family.

In the early 1850s, Baudelaire struggled with poor health, pressing debts, and irregular literary output. He often moved from one lodging to another and maintained an uneasy relationship with his mother, frequently imploring her by letter for money. (Her letters to him have not been found.) He received many projects that he was unable to complete, though he did finish translations of stories by Edgar Allan Poe which were published in Le Pays. Baudelaire had learned English in his childhood, and Gothic novels, such as Lewis's The Monk, and Poe's short stories, became some of his favorite reading matter, and major influences.

Upon the death of his stepfather in 1857, Baudelaire received no mention in the will but he was heartened nonetheless that the division with his mother might now be mended. Still strongly tied to her emotionally, at thirty-six he wrote her: "believe that I belong to you absolutely, and that I belong only to you".

Baudelaire was a slow and fastidious worker, often sidetracked by indolence, emotional distress and illness, and it was not until 1857 that he published his first and most famous volume of poems, Les Fleurs du mal (The Flowers of Evil), originally titled Les Limbes. Some of these poems had already appeared in the Revue des deux mondes (Review of Two Worlds), when they were published by Baudelaire's friend Auguste Poulet Malassis, who had inherited a printing business at Alençon. The poems found a small, appreciative audience, but greater public attention was given to their subject matter. Flaubert, recently attacked in a similar fashion for Madame Bovary (and acquitted), was impressed and wrote to Baudelaire: "You have found a way to rejuvenate Romanticism... You are as unyielding as marble, and as penetrating as an English mist". The principal themes of sex and death were considered scandalous. He also touched on lesbianism, sacred and profane love, metamorphosis, melancholy, the corruption of the city, lost innocence, the oppressiveness of living and wine. Notable in some poems is Baudelaire's use of imagery of the sense of smell and of fragrances, which is used to evoke feelings of nostalgia and past intimacy. The book, however, quickly became a byword for unwholesomeness among mainstream critics of the day. Some critics called a few of the poems "masterpieces of passion, art and poetry" but other poems were deemed to merit no less than legal action to suppress them. J. Habas writing in Le Figaro, led the charge against Baudelaire, writing: "Everything in it which is not hideous is incomprehensible, everything one understands is putrid". Then Baudelaire responded to the outcry, in a prophetic letter to his mother:

"You know that I have always considered that literature and the arts pursue an aim independent of morality. Beauty of conception and style is enough for me. But this book, whose title (Fleurs du mal) says everything, is clad, as you will see, in a cold and sinister beauty. It was created with rage and patience. Besides, the proof of its positive worth is in all the ill that they speak of it. The book enrages people. Moreover, since I was terrified myself of the horror that I should inspire, I cut out a third from the proofs. They deny me everything, the spirit of invention and even the knowledge of the French language. I don't care a rap about all these imbeciles, and I know that this book, with its virtues and its faults, will make its way in the memory of the lettered public, beside the best poems of  V. Hugo, Th. Gautier and even Byron." 

Baudelaire, his publisher and the printer were successfully prosecuted for creating an offense against public morals. They were fined but Baudelaire was not imprisoned. Six of the poems were suppressed, but printed later as Les Épaves (The Wrecks) (Brussels, 1866). Another edition of Les Fleurs du mal, without these poems, but with considerable additions, appeared in 1861. Many notables rallied behind Baudelaire and condemned the sentence. Victor Hugo wrote to him: "Your fleurs du mal shine and dazzle like stars... I applaud your vigorous spirit with all my might". Baudelaire did not appeal the judgment but his fine was reduced. Nearly 100 years later, on May 11, 1949, Baudelaire was vindicated, the judgment officially reversed, and the six banned poems reinstated in France.

By 1859, his illnesses, his long-term use of laudanum, his life of stress and poverty had taken a toll and Baudelaire had aged noticeably. But at last, his mother relented and agreed to let him live with her for a while at Honfleur. Baudelaire was productive and at peace in the seaside town, his poem Le Voyage being one example of his efforts during that time. In 1860, he became an ardent supporter of Richard Wagner. His financial difficulties increased again, however, particularly after his publisher Poulet Malassis went bankrupt in 1861. In 1864, he left Paris for Belgium, partly in the hope of selling the rights to his works and also to give lectures. His long-standing relationship with Jeanne Duval continued on-and-off, and he helped her to the end of his life. Baudelaire's relationships with actress Marie Daubrun and with courtesan Apollonie Sabatier, though the source of much inspiration, never produced any lasting satisfaction. He smoked opium, and in Brussels he began to drink to excess. Baudelaire suffered a massive stroke in 1866 and paralysis followed. The last two years of his life were spent, in a semi-paralyzed state, in "maisons de santé" in Brussels and in Paris, where he died on August 31, 1867. Baudelaire is buried in the Cimetière du Montparnasse, Paris.

Many of Baudelaire's works were published posthumously. After his death, his mother paid off his substantial debts, and at last she found some comfort in Baudelaire's emerging fame. "I see that my son, for all his faults, has his place in literature". She lived another four years.