Pierre Etienne Theodore Rousseau was born on April 15, 1812. His parents were part of the rising successful merchant class, who recognized their son's interest in nature and art and did their best to encourage it. As a young boy, Rousseau spent a great deal of time in the Bois de Boulogne, and at the age of thirteen was sent to the country, in the Franche Comte, where he sketched his surroundings at every opportunity. On his return to Paris a year later, his work showed such improvement and promise that his parents allowed him to choose painting as his profession. Encouraged by his family, Rousseau began studying in earnest, primarily at the studio of Jean Charles Joseph Remond. Even at this early age, Rousseau made frequent excursions in and around Paris including Fontainebleau. Like many Barbizon artists, Rousseau spent a great deal of time in the Louvre copying the Dutch 17th century landscape artists. He also exhibited his first painting at the Salon of 1831. This painting, a landscape from his recent trip to the Avergne, hung high on the wall of the Salon and received only slight and scattered praise. Rousseau spent the next year on the Normandy Coast with several other artists, including Paul Huet, the predominant landscape artist of the time. Huet exerted a strong influence on Rousseau, and encouraged his young pupil to draw directly from nature.

It was in the 1830s that Rousseau became acutely aware of the English romantic painters, especially John Constable and Richard Parkes Bonington. In 1832, Rousseau travelled extensively in Normandy and Brittany and the following year received his first real public recognition through the purchase of a picture at the Salon by the Duc d'Orleans. During the winter of 1833 34, he spent his first significant period at Fontainebleau. Rousseau's greatest involvement with the Salon occurred between the years 1834 1836. In 1834 he won a third class medal, and in 1835 two of Rousseau's sketches were purchased by the Prince de Joinville. Throughout the rest of the decade and into the 1840s, he spent a great deal of time travelling in the French countryside and an increasing part of this time at Barbizon, often with his closest friend, Jules Dupre. During this time, Rousseau exhibited frequently at the Salon des Refusees, becoming a well known but controversial landscape painter.

Rousseau established a permanent studio at Barbizon in 1848, and in June of the following year he met Millet, who had also moved to Barbizon, and this would mark the beginning of their friendship that would last a lifetime. The Barbizon School was growing in popularity and importance in the early 1850s, in part because of the support of Americans who were purchasing many of Millet's works at the Salon. Rousseau's time at Barbizon was dedicated to new pictures and reworking old canvases, but also to other pursuits, and he became an accomplished botanist, geologist, and meteorologist. 

Initially, Rousseau's landscapes were somewhat hard and severe. They were often rocky and dark and frequently set within the forest. These pictures were eventually supplanted by the style that predominates perhaps some of his best known paintings. The pictures became softer, lighter, and were generally considered more Romantic. Though success had followed Rousseau from the end of the 1840s, by the late 1850s his fortunes began to decline. He was spending most of his money to purchase Old Master prints by German and Dutch masters, most notably Durer and Van de Velde, as well as on his new found passion—Japanese prints. Rousseau was profoundly interested in their flatness and color, and he immediately set about repainting old canvases and beginning new ones. His pictures from this period show a great flatness and a sense of Oriental atmosphere in color. It has also been suggested that the influence of Japanese art was not only of visual importance for Rousseau, but that he, as the Japanese, shared the important concept that man was one with nature.

By 1865, Rousseau's fortune was again on the rise, though his health was failing. In 1867, at perhaps the height of his popularity and with the favor of Napoleon III, Rousseau became the head of an international jury at the Universal Exhibition. In the same year, a major exhibition of his work was held, but by this time Rousseau's health was deteriorating rapidly and Millet cared for him until his death on December 22, 1867.