The Alexander technique, named after its developer Frederick Matthias Alexander (1869–1955), is a pseudoscientific alternative therapy based on the idea that poor posture causes a range of health problems. The American National Center for Complementary and Integrative Health classifies it as a "psychological and physical" complementary approach to health when used "together with" mainstream conventional medicine.

Alexander began developing his technique's principles in the 1890s to address his own voice loss during public speaking. He credited his method with allowing him to pursue his passion for performing Shakespearean recitations.

Proponents and teachers of the Alexander technique believe the technique can address a variety of health conditions, but there is a lack of research to support the claims. As of 2021^[update], the UK National Health Service and the National Institute for Health and Care Excellence (NICE) cite evidence that the Alexander technique may be helpful for long-term back pain and for long-term neck pain, and that it could help people cope with Parkinson's disease. Both the American health-insurance company Aetna and the Australian Department of Health have conducted reviews and concluded that there is insufficient evidence for the technique's health claims to warrant insurance coverage.

The Alexander technique is most commonly taught in a series of private lessons which may last from 30 minutes to an hour. The number of lessons varies widely, depending on the student's needs and level of interest. Students are often performers, such as actors, dancers, musicians, athletes and public speakers, people who work on computers, or those who are in frequent pain for other reasons. Instructors observe their students, and provide both verbal and gentle manual guidance to help students learn how to move with better poise and less strain. Sessions include chair work – often in front of a mirror – during which the instructor will guide the student while the student stands, sits and walks, learning to move efficiently while maintaining a comfortable relationship between the head, neck, and spine, and table work or physical manipulation.

In the United Kingdom, there is no regulation for who can offer Alexander technique services. Professional organisations do exist, however, typically offering three-year courses to people becoming instructors.

The Alexander technique is based on the personal observations of Frederick Matthias Alexander (1869–1955). Alexander's career as an actor was hampered by recurrent bouts of laryngitis, but he found he could overcome it by focusing on his discomfort and tension, and relaxing. Alexander also thought posture could be improved if a person became more conscious of their bodily movements.

While on a recital tour in New Zealand (1895), Alexander came to believe in the wider significance of improved carriage for overall physical functioning, although evidence from his own publications appears to indicate it happened less systematically and over a long period of time.

Alexander did not originally conceive of his technique as therapy, but it has become a form of alternative medicine.