The Online Doctor Appointment System is an open-source web application developed using PHP, HTML, CSS, and MySQL. It allows patients to book medical appointments online with doctors from clinics or hospitals. The system provides three roles: Admin, Doctor, and Patient. Admins can manage doctors and appointments, doctors can view and manage their schedules and patient details, while patients can book appointments, view previous bookings, and manage their account. The project is designed to simplify the appointment scheduling process for both patients and healthcare providers.