The Montessori method is an educational method for children, based on theories of child development originated by Italian educator Maria Montessori in the late 19th and early 20th century. It is applied primarily in preschool and elementary school settings, though some Montessori high schools exist.

The method is characterized by an emphasis on self-directed activity on the part of the child and clinical observation on the part of the teacher (often called a "director", "directress", or "guide"). It stresses the importance of adapting the child's learning environment to his or her developmental level, and of the role of physical activity in absorbing academic concepts and practical skills. It is also characterized by the use of autodidactic (self-correcting) equipment to introduce various concepts.

Although there are many schools which use the name "Montessori," the word itself is not recognized as a trademark, nor is it associated with a single specific organization.

Dr. Maria Montessori developed what became known as "The Montessori Method" as an outgrowth of her post-graduate research into the intellectual development of children with mental retardation. Building on the work of French physicians Jean Itard and Edouard Seguin, she attempted to build an environment for the scientific study of children with various sorts of physical and mental disabilities. Following successes in the treatment of these children, she began to research the application of her techniques to the education of children of average intelligence. By 1906, Dr. Montessori was sufficiently well-known that she was asked to run a day-care center in the run-down San Lorenzo district of Rome. She used the opportunity to observe the children's interactions with materials she developed, refining them as well as developing new materials with which the children could work. This materials-centered approach, in which the teacher primarily observes while the children select materials designed to impart specific concepts or skills, is a hallmark of Montessori education. Montessori's initial work was primarily with preschool-aged children. After observing developmental changes occurring in children who are just beginning elementary school, she and her son Mario began a new course of research into adapting her approach to elementary-aged children. Toward the end of her life, in her book From Childhood To Adolescence, Montessori sketched out a view of how her teaching methodology might be applied to the secondary and university levels.

The premises of a Montessori approach to teaching and learning include the following:

• That children are capable of self-directed learning.
  
• That it is critically important for the teacher to be an "observer" of the child instead of a lecturer. This observation of the child interacting with his or her environment is the basis for the ongoing presentation of new material and avenues of learning. Presentation of subsequent exercises for skill development and information accumulation are based on the teacher's observation that the child has mastered the current exercise(s).
  
• That there are numerous "sensitive periods" of development (periods of a few months or even weeks), during which a child's mind is particularly open to learning specific skills or knowledge such as crawling, sitting, walking, talking, reading, counting, and various levels of social interaction. These skills are learned effortlessly and joyfully. Learning one of these skills outside of its corresponding sensitive period is certainly possible, but always difficult and frustrating.
  
• That children have an "absorbent mind" from birth to around age 6, possessing limitless motivation to achieve competence within their environment and to perfect skills and understandings. This phenomenon is characterized by the young child's capacity for repetition of activities within sensitive period categories, such as exhaustive babbling as language practice leading to language competence.
  
• That children are masters of their school room environment, which has been specifically prepared for them to be academic, comfortable, and to encourage independence by giving them the tools and responsibility to manage its upkeep.
  
• That children learn through discovery, so didactic materials with a control for error are used. Through the use of these materials (specifically designed toys, blocks, sets of letters, science experiments, etc.) children learn to instinctually correct their own mistakes instead of rely on a teacher to give them the correct answer.
  
• That children most often learn alone during periods of intense concentration. During these self-chosen and spontaneous periods, the child is not to be interrupted by the teacher.
  
• That the hand is intimately connected to the developing brain in children. Children must actually touch the shapes, letters, temperatures, etc. that they are learning about - not just watch a teacher or TV screen tell them about these discoveries.