An Introduction to Theory and Practice of Guidance and Counselling is a comprehensive textbook designed to provide foundational and advanced knowledge in the field of guidance and counselling. Structured into fourteen detailed sections, this work explores core concepts, historical development, service components, theories, applications, and practical implementation of guidance and counselling programmes in schools and other institutional settings. The book begins by distinguishing between guidance and counselling, followed by a deep dive into the development of these practices, including their integration into the national education policy. It outlines essential school counselling services such as orientation, information dissemination, referral, follow-up, and evaluation. Each section covers relevant theories including client-centered, psychoanalysis, behavioral, Gestalt, existential, RET, and eclectic theories highlighting their practical application in school settings. Special attention is given to critical areas such as study skills, career education, sex education, marriage counselling, psychological testing, health counselling (including drug abuse, alcoholism, and smoking), and strategies for setting up functional school guidance programmes. With accessible language and real-world application strategies, the book serves as an invaluable resource for students, educators, trainee counsellors, and practitioners in educational and mental health fields.