A Public-Private Partnership (PPP) is a long-term agreement between a government and a private sector institution, typically involving private capital financing public projects and services, with revenues later drawn from taxpayers or users. These arrangements, which became prominent around the late 20th century, are primarily used for infrastructure such as schools, hospitals, and transport systems, often to keep projects off government balance sheets. However, PPPs are generally more expensive than publicly financed projects due to the private sector's higher cost of borrowing and significant transaction costs, with these expenses ultimately borne by the public.

PPPs are a subject of considerable controversy, facing criticism for their lack of financial transparency, concerns over the public's return on investment, and mixed evidence regarding their efficiency and value for money. While advocates highlight benefits like risk-sharing and innovation, critics often point to disproportionately high costs and accountability issues. This debate is further complicated by the absence of a universally agreed-upon definition for PPPs, which can encompass hundreds of different contractual arrangements.