Psychosynthesis is an approach to human development fostered by Roberto Assagioli (1888-1974) beginning around 1910 and continuing to the present day. It is both a theory and practice where the focus is to achieve a synthesis, a coming together, of the various parts of an individual's personality into a more cohesive self. That person can then function in a way that is more life-affirming and authentic. Another major aspect of psychosynthesis is its affirmation of the spiritual dimension of the person, i.e. the "higher" or "transpersonal" self. The higher self is seen as a source of wisdom, inspiration, unconditional love, and the will to meaning in our lives.

Psychosynthesis is founded on the basic premise that we participate in an orderly universe structured to facilitate the evolution of consciousness. A corollary is that each person's life has purpose and meaning within this broader context and that it is possible for the individual to discover this.

Psychosynthesis has had a profound impact on the human potential movement. For example, the use of guided imagery and the concept of subpersonalities within the context of Psychosynthesis brought out an appreciation of their value and significance, so that these tools are now in common use.