Owning private islands became a symbol of extreme wealth in the 20th century, but the practice has earlier roots in colonial land acquisitions, when empires granted or sold entire islands to private individuals for agriculture, trade, or strategic control. In the modern era, the market for private islands expanded in the 1950s and 1960s as aviation improved and remote coastal regions became more accessible, turning islands into luxury real-estate assets. Countries such as the Bahamas, Seychelles, Fiji, and parts of Europe created legal frameworks allowing foreign buyers to purchase or lease islands, often with specific environmental or zoning conditions. Today, private islands are traded through specialized brokers and international property firms, treated much like high-value estates with their own titles, regulations, and offshore ownership structures. The concept intersects with maritime law, exclusive economic zones, and sovereignty questions, since islands sometimes border strategic waters or contain ecosystems governed by national conservation rules. The rise of billionaire ownership in the 21st century coincides with global wealth concentration, new tax havens, and increased demand for secluded properties, making private island ownership not only a luxury trend but a complex issue tied to property rights, national jurisdiction, and global inequality.