A project proposal letter is an official document that outlines the intent of a potential project. It is often sent by businesses, organizations, or individuals to prospective sponsors or partners who can help bring the project to fruition. The proposal should include an overview of the project, key objectives and goals, implementation details, budget, timeline and expected deliverables. It should also describe the benefits and value that the potential partner or sponsor will gain from investing in this project. When written with care and thoughtfulness, a project proposal letter can be an effective tool for garnering support and resources.