This project details the system design for a hotel online reservation system, encompassing the planning and design phases. The planning phase includes project identification, feasibility studies, business descriptions, and the System Development Life Cycle (SDLC) methodology. It outlines business and functional requirements, defines the project scope, and presents UML use case diagrams, detailed use cases for reservation and booking systems, and model processes. The logical and physical data flow diagrams, along with a context-level data flow diagram and model data design, are also included. A sequence diagram illustrates the interactions within the system. The design phase covers architecture design, interface structure design, and data storage design, culminating in a physical entity-relationship diagram. The project utilizes diagrams and models to analyze and design the system, adhering to the requirements of a CSIS 351 course assignment. The project aims to enhance the hotel's online booking process, improving customer service and operational efficiency.