Nicholas Culpeper (18 October 1616 - 10 January 1654) was an English botanist, herbalist, physician, and astrologer. His published books, The English Physitian (1652) and the Complete Herbal (Complete Herbal (Wordsworth Reference) (1653), contain a rich store of pharmaceutical and herbal knowledge.

Culpeper spent the greater part of his life in the English outdoors cataloguing hundreds of medicinal herbs. He criticized what he considered the unnatural methods of his contemporaries, writing: "This not being pleasing, and less profitable to me, I consulted with my two brothers, DR. REASON and DR. EXPERIENCE, and took a voyage to visit my mother NATURE, by whose advice, together with the help of Dr. DILIGENCE, I at last obtained my desire; and, being warned by MR. HONESTY, a stranger in our days, to publish it to the world, I have done it."

Culpeper was the son of Nicholas Culpeper (Senior), a clergyman. He studied at Cambridge, and afterwards became apprenticed to an apothecary. After seven years his master absconded with the money paid for the indenture, and soon after this, Culpeper's mother died of breast cancer. Culpeper married the daughter of a wealthy merchant, which allowed him to set up a pharmacy in the halfway house in Spitalfields, London, outside the authority of the City of London at a time when medical facilities in London were at breaking point. Arguing that "no man deserved to starve to pay an insulting, insolent physician", and obtaining his herbal supplies from the nearby countryside, Culpeper was able to provide his services for free. This, and a willingness to examine patients in person rather than simply examining their urine (in his opinion, "as much piss as the Thames might hold" did not help in diagnosis), Culpeper was extremely active, sometimes seeing as many as forty people in one morning. Using a combination of experience and astrology, Culpeper devoted himself to using herbals to treat the illnesses of his patients.

During the early months of the English Civil War he was accused of witchcraft and the Society of Apothecaries tried to rein in his practice. Alienated and radicalised, in August 1643, he joined a train band and fought at the First Battle of Newbury. There he carried out battlefield surgery, Culpeper was taken back to London after sustaining a serious chest injury from which he never recovered. There, in co-operation with the Republican astrologer William Lilly, he wrote the work 'A Prophesy of the White King', which predicted the king's death.

Influenced during his apprenticeship by the radical preacher John Goodwin, who said "no authority was above question", Culpeper became a radical republican and opposed the "closed shop" of medicine enforced by the censors of the College of Physicians. In his youth, Culpeper translated medical and herbal texts such as the 'London Pharmacopaeia' from the Latin for his master. It was during the political turmoil of the English civil war, when the College of Physicians was unable to enforce their ban on the publication of medical texts, that Culpeper deliberately chose to publish his translations in vernacular English as self-help medical guides for use by the poor who could not afford the medical help of expensive physicians. Follow-up publications included a manual on childbirth and his main work, 'The English Physician', which was deliberately sold very cheaply, eventually becoming available as far afield as colonial America. It is the most successful non-religious English text ever, and has been in print continuously since the 17th century.

Culpeper believed medicine was a public asset rather than a commercial secret, and the prices physicians charged were far too expensive compared to the cheap and universal availability of nature's medicine. He felt the use of Latin and expensive fees charged by doctors, lawyers and priests worked to keep power and freedom from the general public. Three kinds of people mainly disease the people priests, physicians and lawyers priests disease matters belonging to their souls, physicians disease matters belonging to their bodies, and lawyers disease matters belonging to their estate. Culpeper was a radical in his time, angering his fellow physicians by condemning their greed, unwillingness to stray from Galen and their use of harmful practices such as toxic remedies and bloodletting. The Society of Apothecaries were similarly incensed by the fact that he suggested cheap herbal remedies as opposed to their expensive concoctions. His influence is demonstrated by the existence of a chain of "Culpeper" herb and spice shops in the United Kingdom, India and beyond, and by the continued popularity of his remedies among New Age and alternative holistic medicine practitioners.

Culpeper attempted to make medical treatments more accessible to layperson by educating them about maintaining their health. Ultimately his ambition was to reform the system of medicine by questioning traditional methods and knowledge and exploring new solutions for ill health. The systematization of the use of herbals by Culpeper was a key development in the evolution of modern pharmaceuticals, most of which originally had herbal origins.

Culpeper's emphasis on reason rather than tradition is reflected in the introduction to his Complete Herbal (Wordsworth Reference) , though his definition of reason was not that different from the Romantic philosophies of the era presenting nature as refuge. Culpepper paired the plants and diseases with planetary influences, countering illnesses with nostroms that were paired with an opposing planetary influence. Combining remedial care with Galenic humoral philosophy and questionable astrology, he forged a strangely workable system of medicine; combined with his "Singles" forceful commentaries, Culpeper was a widely read source for medical treatment in his time.

He died of tuberculosis in London on 10 January 1654 at the age of 38. Only one of his eight children, Mary, survived to adulthood.