A "Phantom Read" occurs in database systems when a transaction reads a set of rows that match a certain condition, but another transaction inserts or deletes rows that meet the same condition before the first transaction completes. This can lead to inconsistencies, as the first transaction may not see the newly added or removed data, resulting in an incomplete view of the database. Phantom Reads are a type of concurrency issue that can arise in systems using the SQL language. To prevent Phantom Reads, database systems often implement isolation levels, such as Serializable, which ensures that transactions are executed in a way that avoids these anomalies.