Imagine walking up to a bank teller in a new country. You have no passport, no driving licence — but the teller still knows who you are, trusts your identity, and opens an account in seconds. That is the promise of well-designed digital identity systems. In this chapter, we explore the real-world identity frameworks that governments, businesses, and global bodies have built, the heated debates around them, and the design choices that make them either a bridge to financial services or a wall that shuts people out.