Lamarck was born at Bazentin-le-Petit, Picardy, North of France, on August 1, 1744. He was the youngest of 11 children, born to noble parents in rural France of that time. His family had a strong military background with several generations having served as officers in the French army. His father Phillipe, wanted him to make a career at the church. The young Lamarck entered the Jesuit seminary at Amiens around 1756, but not long after his father's death, Lamarck rode off to join the French army campaigning in Germany in the summer of 1761; in his first battle, he distinguished himself for bravery under fire and was promoted to officer. After peace was declared in 1763, Lamarck spent five years on garrison duty in the south of France, until an accidental injury forced him to leave the army. The accident was the result of a game that the soldiers were playing for relaxation during peacetime. One of the soldiers lifted Lamarck off the ground by his head causing serious inflammation in the neck.

Surgery in Paris worsened his state and he had to be decommissioned. Relieved from the army, he fell back to studying the natural sciences. To earn a living, he began working as a clerk in a bank that provided him the necessary time and means to read botanical works. He gave personal tuitions to the son of the great botanist – Buffon. With Buffon’s help, he published a book on plants of France, Flore Francaise in 1778. He was then elected to the prestigious French Academy of Sciences with backing of Buffon. He toured Europe in search of new botanical specimens and returned to start and keep up the Royal herbarium at Jardin des Plantes. To supplement his poor salary, required him to seek additional income through teaching. He continued research and produced various works on botany, physics and meteorology till the time ill health forced him to retire.

Lamarck married thrice. He is rumored to have married and widowed the fourth time, but no documentary evidences exist to support such claim. 

He married Marie Delapoute in 1792. They had been living together since 1777 and when Lamarck married her, she was on her deathbed and was the mother of his first six children. He married the second time, to Charlotte in 1795. She too died in 1797. His third wife whom he married in 1798 left him in 1819. By this time Lamarck had to retire from his botanical works as his eyesight began to seriously deteriorate. He died on December 18, 1829 in Paris. In the last ten years of his life he was blind, penniless and removed from all scientific activity. The two daughters who tended him on his deathbed were left penniless at his death; one surviving son was deaf and handicapped and another insane. Only one son, Auguste, was successful as an engineer, and went on to marry and have children. Such was the state of his family when he died that they had to apply to the Academy for financial assistance. Lamarck’s books and the contents of his home were auctioned. He was buried in a temporary line pit – whose remains were exhumed every five years or so. It was later piled up in the Paris catacomles, anonymously, alongside the impoverished, vagrant and unnamed dead.